You've probably seen people do it in the movies, but Art of Manliness notes that there are a few things you'll want to make sure of before you go kicking down every door in your path:
Check to see which way the door opens by checking the hinges. If the door opens towards you, kicking it down is going to be next to impossible. Kicking a door down is best employed on a door that swings away from you.
Kick to the side of where the lock is mounted (near the keyhole). This is typically the weakest part of the door.
The above infographic explains most of the things you need to know, but for a more detailed description of the process, hit the link below.