The first thing to do is reduce your portions. Now this may seem hard, but I promise you it's really not. Especially when your body starts getting used to eating less. Americans today often eat well beyond their body's needed amount of calories in one meal.
Ever feel bloated, overly full, and gross after a meal? It's because you ate too much, and you know it. This often happens at picnics, potlucks, and holiday dinners.
If you reduce your intake of so much food, however, you will notice a difference.
One main thing I suggest is to use smaller plates, bowls, etc. Using these smaller dishes allows you to fill them up all the way and trick your brain into thinking you are eating more than you actually are. Sometimes measuring your food is helpful as well so you know how much you are consuming and you can more easily count your calories, if you choose to do so.
I can tell you, I've been starting to implement this and it really makes me feel so much better throughout the day. The best way to eat is in 200 calorie or less increments.
One last thing: I encourage you to refrain from seconds. It takes about 20 minutes for food to fully digest and hit your stomach. So if you don't feel entirely full after your first plate of food, give it some time and see how you feel.