I used to learn martial arts, so you can be sure the info in this post is legit. Please FOLLOW IT. I see fist fights written incorrectly, and it irks me to no end.

1. When you get hit in the face, it HURTS!
Even when wearing a helmet, getting punched in the face jostles you. Your vision gets fuzzy for a second as your brain tries to make sense of what's happening. It'll hurt for just a few moments before the adrenaline kicks in and numbs it so you can keep going. If your character gets hit in the face, make sure they don't just ignore it and keep on fighting like nothing happened. It happens in movies, but it's very unrealistic.

2. Fighting is mostly REACTION, not thinking!
When you're fighting with someone and are in the heat of throwing punches and kicks (or swords or whatever weapon your character is using), there is NO time to think. It's 99% reaction, 1% conscious thought. You can condition your reactions, though. Do a move a thousand times, and it'll become second nature. If you train yourself to attack with a spin kick when someone comes at you with a punch, you'll do it automatically, without thinking.

Usually, I win about half of my fights, more or less. Once I only had an hour of sleep the night before, and I won EVERY fight. I was moving so fast, and my reactions were right on point. It was astounding, but I realized I was fighting better because I wasn't thinking as I fought, like I usually did. I was simply reacting. When you think, you lose precious time to attack. Your reactions will be slower because you have to think about them first.

All too often, I see fight scenes where the MC is meticulously planning out each move in the heat of battle. That's NOT POSSIBLE. They can plan before the punches start flying, or if there's a short lull in attacks, but never WHILE attacking. Your brain just can't go that fast (at least mine doesn't. There could be people with superhuman brainpower that CAN think while fighting, but generally, so much adrenaline is being pumped into you that it's really hard to think straight. Your body will revert to simple reflexes for the most part. Again, you can train yourself to CHANGE those reflexes.)

3. Fights are not like Mortal Kombat.
You cannot fight at 100% until you die. You WILL get tired. Your muscles WILL hurt, and your reflexes WILL become sluggish. No one can function at 100% for more than a few seconds (again, there are some exceptions, like those people who can max out tredmills and run like 12 miles without breaking too much of a sweat. Those people are rare, so don't make EVERY character like that. Even making one character like that wouldn't be too believable to the general public, so use your discretion). When you're REALLY exhausted but still forced to fight, you can will a few bursts of your 100%, but those will not last too long, and you can't do it too often. You need a LOT of motivation to push harder when you can't breathe and your entire body is on fire from muscle fatigue.

Random biology of exercise: Most active processes in your body, including contracting your muscles, use a molecule called adenosine triphosphate (ATP) as energy. When a phosphate group is cleaved off, energy is released (and the resulting molecule is called adenosine diphosphate, or ADP). Your intramuscular store of ATP is very low, so your body primarily utilizes a metabolic process called anaerobic respiration (which consists of the phosphagen system and glycolysis) to make more ATP. But it's not 100% efficient (about 70-80% of the ATP created is actually given off as heat), so you won't be able to sprint full-out for more than a minute, if even that. If you've ever done or seen the Wingate Anaerobic Test (a person pedals on a special exercise bike full-out for 30 seconds), you'll notice how the force production generally peaks during the first five or ten seconds but then steadily decreases from there. A person cannot sustain their full force production for more than a few seconds unless they're some kind of superathlete because the demand for ATP exceeds the amount you can produce. And even superathletes won't be able to full-out sprint for half an hour.

4. What happens when you get the wind beaten out of you.
The solar plexus is the spot directly below the sternum (the long, vertical bone right in the center of your chest where all the ribs are attaching to. go Google image a picture of a skeleton). There are NO muscles covering this spot. If you can strike someone there, it will deflate their lungs.

Try it (gently) on yourself. Put your finger right in the center of your chest and trace it down until you get past your sternum. Gently press that spot, and you'll feel really uncomfortable.

If someone hits you there, you'll keel over. It will HURT. The pain will subside in a few moments, but it takes longer for your lungs to inflate with air again. This is a slow, terrifying process. For about ten seconds after you can stand up normally again, you will be unable to speak at all. Someone kicked me there once, and they asked if I was okay. I opened my mouth and tried to get words out, but they just wouldn't come out. It was terrifying and fascinating at the same time. The pain was gone, but I couldn't talk at all. I had to take a few really deep breaths before my lungs opened up and I could speak.

So the solar plexus (right below your sternum) is the most efficient spot to hit to wind someone. You can hit them really hard in the gut, too, but since that is covered with your abdominal muscles, it won't always work. Abs are like body armor. They protect your organs. On a well-trained person, they can flex their abs when they're hit, and the blow won't really do anything to them. So never have a character hit a muscly person in the gut and have him/her rolling around on the floor groaning. Usually they'll be able to take it. They may wince or feel a bit of unpleasant-ness, but it won't wind them. They'd have to get hit REALLY hard to get winded from blow to their gut. If they don't have well-developed abs, they may have fat covering it, which is effective, too (not as much as muscle, granted, but you've seen movies where they try to hit a fat person in the gut, and they just bounce off. It doesn't work QUITE that well, but fat does provide a little protection). If the person is just really skinny with no muscle or anything, then hitting them in the gut will wind them without too much force.

5. If you're using weapons (like swords), and you hit each other's weapon head-on, your arm will go numb.
Same thing with shields and the like. Someone rams your arm/hand with a sword, your bones will rattle and feel the shock. The degree of the shock depends on the person attacking, their weapon, and your muscle strength. Muscles not only move your limbs, but they also hold joints together. If you have really strong muscles, you can dampen the shockwave, and it won't hurt as much. If you don't have strong muscles, your arm will go numb and you will become incapacitated for a moment as you fall to the ground in agony. You probably won't be able to hold your weapon as tightly after this. Most likely, you'll drop it or barely be able to keep hold on it.

6. Humans cannot break through rock unscathed. Dragonball Z is unrealistic, guys. :(
There are people who can break through concrete, but that takes a LOT of training. Usually, your charries wouldn't be training to break through cinder blocks or bricks, so don't even go there. You have to really train your hands to become harder. I did break a wooden board on the first try, though, so that's possible for someone who knows the technique. You have to hit PAST the object, not AT it. You'll get more force that way. Same goes for hitting people, too. All trained fighters know that you have to strike past the target. Never aim directly at it.

But yeah, having the MC fall twenty stories and slam into the ground and then stand up again... no. That's not possible.

7. After a hard battle, your characters cannot delicately make love with each other.
You will be in pain, sore, exhausted. No sex or make-out sessions afterwards, please, guys. O___o If someone is beat up, the last thing on their mind is kissing someone. They'll want to collapse on a bed and sleep forever.

8. D.O.M.S
Delayed Onset Muscle Soreness! When you work out really hard, don't you notice how you're most sore not the day after, but TWO days after? If you've never been sore before, SHAME ON YOU. GO TO THE GYM AND EXERCISE! >:(

For one of my exams, they worked us SO hard that the next few days, I couldn't move at all. My friends had to carry my books for me, and I couldn't lift my arms too high. They just wouldn't. They were too stiff, along with the rest of my body. It was terrible, so make sure your charries do get sore after hard workouts or extended fights.

Here's what Wikipedia says about DOMS: "The soreness is perceived as a dull, aching pain in the affected muscle, often combined with tenderness and stiffness. The pain is felt only when the muscle is stretched, contracted or put under pressure, not when it is at rest. Although there is variance among exercises and individuals, the soreness usually increases in intensity in the first 24 hours after exercise, peaks from 24 to 72 hours, then subsides and disappears after about five to seven days after exercise."

Tips from -Luna- about weapons! (I've elaborated on some points, too.)
9. Guns have kicks.
Some big guns have very strong kicks. Lots of people forget to take this into account. Also if someone is firing a gun for the first time, they might actually get knocked over. I've never fired a gun but my dad has and he told me this.

10. Silencers are not silent.
The movies like to pretend they are, but really they just muffle the noise a little bit. If you want to be realistic, then don't pretend that you can hide around a corner and snipe someone, and that people in the same room won't notice if they don't look. It doesn't work that way.

11. A fight between well-trained opponents will only last a few seconds.
ONLY A FEW SECONDS. I'm dead serious. Getting hit once is crippling, and if the other person is good enough, they'll use that moment to really slam you hard. You'll lose. Generally the first person to land a hit will win. Fights are not like animes where you battle for hours.

Real swordfights do not take very long, as people get tired, and it takes a lot of energy to wield a sword, and of course a hit with a sword is not something you are going to easily recover from. If a swordfight takes a long time it is likely not because both sides are masters, but because they are dunces.

12. Arrows hit things HARD.
If you hit an apple with an arrow, if there is no backstop, the arrow will not go neatly halfway through the apple. The apple will fall into little tiny bits. Needless to say, a person cannot just pull an arrow out of their shoulder and keep fighting unless they are some kind of superhuman. Arrows are not blowdarts or toothpicks. I say this as a person who has shot a bow. Also, it is very hard to draw a bow.

Back to Yuff
13. It takes a LOT of strength to draw a bow.
A person has to train for years before they can effectively use a bow and arrow. A person cannot learn this in just a few hours or even a few weeks. Same goes for any other weapon, but especially with bows and arrows. Swords are HEAVY. Even light ones will take a toll on their wielder. The person has to train with their weapon for years before they become very good with it. Whether or not they have talent as a swordsman is irrelevant. Their muscles will still never be strong enough initially to properly wield a sword (or whatever their weapon of choice), and that strength comes from thousands of hours of training and conditioning.

From Pheonix Rising
14. Crossbows cannot be fired quickly.
You have to pull the drawstring back and lock it. It requires some upper body strength in the shoulders and abs, but not as much as it would to pull a bow. You cannot walk around with the bowstring drawn and with the crossbow bolt (arrow) loaded, just like walking around with a regular bowstring drawn will put too much continuous strain on the bow. If a crossbow is locked and loaded, and you still have it at your feet where you were pulling it up, you'll shoot yourself in the face :P Size varies, of course, but they require less skill in aiming and speed than a regular bow. When armies are short on bowmen and don't have time to train more, they give men the crossbow. It's "easy" to operate... but I don't think it has the same range or accuracy as a trained bowman would have with a long or recurve bow.

They're good weapons for those up on the ramparts firing down below, but not a heat-of-battle weapon. Unless you're being charged by a crazy Viking who is giving you plenty of time to pull back the bowstring, load the bolt, take aim, and fire. (They also have a bit of a kick, like a gun.)

From Katie6425
15. Stuff about guns.
Most guns do not kick (as long as you are the right size, a 6 year old shooting a 10 gauge is obviously going to hurt) but if you hold the gun the poach above your armpit you will not get kicked. Another thing is, when you are in the heat of the moment (in my case hunting) guns aren't loud. Afterwards you won't even remember the sound, nor will your ears ring, your' subconscious blocks it out so don't throw anything about that in. And please..please no what you are talking about when using guns. Putting a silencer on a revolver does nothing because it's not a sealed gun. A silencer absorbs gases that protrude from the barrel. On a revolver it can come out all over because it doesn't use a magazine. And when you shoot guns, experienced users squeeze the trigger rather than just pull because than the gun kicks up and you..well miss. And they always keep there eyes on the sights until they see the animal/person fall. Another thing is not all guns have scopes, and even if it does they aren't automatically sighted in. (which means if you aim at an apple on someones head with a scope you just put on, you won't hit it.) I see so many books were they pick up a gun and fire and it's perfect. Perhaps the thing that shows the most inexperience gun use in a writer is when they use generic words like "pistol" "shotgun" "rifle." Okay, you don't have to say "marlin model 60 7 millimeter 08 Remington" but at least say "Remington, Rugar, Marlin, Savage, Winchester.." Just think about when you are describing a car, you don't say "the car" you say chevy, ford, honda, etc. One last thing, guns do not have an unlimited amount of bullets! No when to reload!

From Kat De Rosa
16. Stuff about archery.
If you are having problems drawing a bow, it is because you aren't using the correct one. There are different types of bows for different people. It's very hard for me to draw my dads bow because the pull of the string is much tighter than my own. So the draw weight is what you have to look at. A beginner can pull back say 30-40lbs, while a more advance hunter say 70lbs. Weight is the big thing that determines if the draw is harder to do. It normally goes from 30-70lbs for adults and less for kids. Draw lengths needs to be taken into consideration because it has to fit your arm, but when you buy a bow the salespeople or professionals normally help you with that.

I can, without much effort string, draw my bow-it might because I'm physically fit and have been doing archery for a number of years. I'm even in my colleges archery club. However, if your character is girl and drawing back a weight of 30-45lb then that will be easy for her to do, but if she's trying to pull back at 60-70lbs that will be really hard unless she's all muscle and very strong.

There is also a difference between competitive and hunting bows. I use a compound bow, which allows sights, scopes, and so forth, while other types don't have those. So it might be good to say the different type of bow-compound, long, and recurve are generally the most common.

Also, you need to wear a brace, which is a technically an arm-guard to protect the inside of your arm from being hit by the string. If you've ever been hit by a sting, it hurts like mother, and it leaves a nasty bruise. I've had one that lasted for two weeks. You won't continue once hit, ad you'll mostly likely drop the bow. The first time I did it, I scream bloody hell. I also use a shooting glove, which removes sweaty from hands and helps making sure you don't slip when drawing the bow.

From Supernatural35
17. More on guns!
Guns: Some guns (like the Beretta) can hurt you if you don't handle them well. For example, the aforementioned Beretta can nick the gun holder if they're holding it wrong or haven't familiarized themselves with the weapon. It's called "Baretta Bite" and will leave a gash in your hand, usually between the thumb and trigger finger. If your character is randomly holding a gun they've never seen before, they might hurt themselves!

Also, in the holding of said gun: There is a REASON that law enforcement officers hold their guns a certain way: It's accurate and a stable hold on a gun. If a character is holding a gun with one hand pushing forward with the other on top of it pulling it back, it creates a stable platform that will make the shot more accurate.

The 'gangster hold' where they shoot from the hip? Unreliable, random, and usually only looks cool to people who have never shot a gun. You can't aim it from your hip, it's unstable, and you might end up accidentally shooting yourself in the foot.

The 'kill shot' is a MYTH. DO NOT turn the gun to the side when a character shoots. It decreases accuracy, though it does admittedly looks cool XD

The other more accurate, more casual way to hold a gun is a straight arm with a locked wrist, a solid line with your arm. It's stable, less accurate than the push-pull hold but still relatively accurate, and allows you to look straight down the sight of the gun to your target.

From Page264
18/19. Throat strikes and drugs + pain.
Another way to effectively wind someone is to punch them in the throat. NO ONE is getting up from that. At least not right away.

Pain doesn't always apply for people who are on something. For instance, a drunk can fight for a while without stopping because they usually can't feel the pain. Same thing goes for people who are on super high adrenaline rushes and/or drugs.

 From Tempus1Fugit

20. Black-Powder Guns

1. This is a weapon widely used all the way up to WWI. Please don't give people from the American Civil War, ect., machine guns. Seriously, guys, it's not funny and it just shows how you don't really know what's going on in that time period.

2. You DO NOT just pull a trigger for this gun to work. First, you must measure out the black powder with a powder measure and put it into the barrel of the gun. Then you center the pillow ticking patch over the barrel and use a ball starter to start pushing the ball down. If you use a rifle, then your need to start shoving the lead bullet down the barrel of the gun with a short-starter and finish loading the gun with a ram-rod (not sure how to spell these, I've only said them before). Once you can shove the ram rod down so hard that it bounces back out of the barrel, then the bullet is down as far as it can go. Then you need to cock the rifle and put the percussion cap on top of the "nipple" (some guns don't have this, chose your gun wisely). And THEN you can finally pull the trigger and shoot it. When I first shot a rifle, it took me FOREVER to load it, and then the ball can still roll out of the gun if you aren't holding it correctly and that's just annoying...it takes a lot of training and time to be able to load it efficiently and quickly.

3. When you finally shoot it, there is a kick to it, and black powder does shoot out of the barrel of the gun. Have you ever wondered why, in historical movies, there's always a fog over the field? It's not just because of the cannons. Each gun shoots out a lot of ash every time it is fired. Also, the kick that the gun I used had was about three inches to the left and two inches to the ground. Your character is going to know your gun before he can get bulls-eye. They can't just pick up a gun and shoot it properly. Unless they are a Mary-sue, they will miss the shot.

4. There are many different guns, all according to what the time of your historical story is. To write the scene properly, research your gun first and then write about it. Trust me, a lot of historical nerds will love it when you get your black-powder stuff right. ;)