Step 1: Disclaimer (Safety)
1. Keep your guns under or around 400 FPS (Exceptions: Snipers)
2. Have the judgement not to shoot people point blank or within close range (Ask them to surrender or do courtesy kills.)
3. ALWAYS wear goggles or a paintball facemask. (ANSI certified)
4. Don't take off your mask until the end of the game.
5. Keep the orange tip on.
And, the big one,
6. NEVER AIRSOFT IN A PUBLIC PLACE!
One of my friends has experience on the last rule. He was airsofting in a frog pond, when a paranoid old lady called the cops on him. He was about 9, using cheap clear springers, and practically the whole police force came. Imagine what would happen if you and a half-dozen friends came over dressed in tactical gear and wielding assault rifles?