Step 1: It's fun!
Step 2: My suggestions
Set limits. Limit the FPS on a gun, or limit the amount of ammo one can carry at a time, things like that.
Don't cheat, ever!
Don't be scared! The more ballsy you are, the better you are. I'm one of those guys that as soon as you say go, I'm dashing straight at the other team; half the time, I don't even use cover!