Airsoft safety can be boiled down to pretty much 3 main areas...
1. PROTECT YOUR EYES!!! Never ever take your eye protection off in game! I lost count of new players having to be told to keep their masks on in game, 1 stray round and your blind in one eye! Protect everything you think is vulnerable, I also wear a lower face mask, not to lower the pain level, I just like having teeth...
2. Gun Safety. Just because it's not a real gun doesn't mean it can't do real damage. Never point your Airsoft gun at anyone you don't intend to shoot. Dry firing in the safe zone is a big nono! All it takes is one stray BB working it's way loose in your case and you could have just shot someone without any eye pro on! The safe zone is supposed to be just that.
3. Watch Your Footing. In game you're running hell for leather firing, keeping your targets in sight when you hit a rabbit hole you didn't see or tree branch that bit higher than you thought. The last game I went too someone had their day ruined by a forced hospital visit. Be aware of what you are moving over. The BB that you just ducked under could have taken you out of the game for 5 minutes, that log you tripped over has just taken you out of the day! A good pair of boots will help here!
All worst case scenarios I know, so don't panic (never seen or heard of someone loose an eye!). Play with yours and other's safety in mind and nothing bad will happen!
Play safe out there!
P.s. Never, Ever, ever, ever take your eye pro off in game, even on a 36 hour milsim and you need to sleep, never take it off... Seriously!