Upon receiving or retrieving a gun check if it's loaded. Know the rules of the game and abide by them. Never remove facemasks or goggles while on the field. Do not play when very tired or hungry. Bring food or money to buy food from field.
Most injuries occur at the end of the day when players are exhausted.
Not even with protection. If barrel needs checking remove from the gun and check. Notify the field owner or manager of any medical conditions, allergies etc. Not really, but it will helps. As with all strenuous exercise participants should stretch and warm up before playing.