When a paintball game is being played, wear your mask at all times. Do not remove your mask in the dead zone if the dead zone is within range of the field. There are no exceptions to this rule. Keep masks on until barrel plugs have been placed back on all loaded guns. Remember that most severe paintball injuries occur because someone removed their mask at an inappropriate time.
Whenever masks are not being worn, all guns should be blocked with a barrel plug or barrel sock. Safeties are good and should be used, but they often fail or are not properly used, and a physical protection from wayward paintballs is a must. Unless everyone has a mask on, do not take out your barrel plugs.
Keep paintball velocities under 300 (and generally under 280) feet per second (FPS). Gun speeds can be timed with a paintball chronograph (available to use at most pro shops), and should be carefully monitored. A paintball that travels at 280 FPS can cause small bruises, while a paintball that travels faster can cause significantly more damage including severe welts and broken skin.
It is strictly forbidden to bring or consume alcohol before or during, the paintball game.
Do not fire if you can't see what you are firing at. Many players are tempted to stick their guns out and fire without looking, but avoid this. Blind firing can lead to accidentally shooting players who are leaving the field, referees, or other things you shouldn't shoot.
Most problems can be avoided if you just use common sense. Don't shoot animal found in the field. Don't shoot private property. Don't look down the barrel of a loaded gun. Don't shoot yourself, etc. If you ever wonder if something might be a good idea, it's not.
During a game, goggles are to be worn at all times by all persons on the playing field and never removed for any reason.