Every story has a conflict, whether it's minor or major. There actually is good and bad examples of what a conflict should be.
Good Examples: Zombies, apocalypse, threat to society, disease, famine, etc...
Bad Examples: "OMG ONE DIRECTION IS COMING TO TOWN AND I DON'T HAVE TICKETS!"
The conflict of your story should fit in and belong with your story. Usually the conflict is what drives the story forward and makes a book interesting. Since conflict is what makes or breaks a book, you should thoroughly develop the conflict and plan outcomes from it.
Some conflict ideas:
-Apocalypse
-Zombies
-Disease
-Famine
-Otherworldly creatures
-Natural Disasters
-Threat to society
-Threat to life
Really, the possibilities are endless. Those ideas were just a few to get you thinking.

Did I miss anything? Comment!