Paintball depending on the type of game you are playing will have different rules to the game. Although these rules for different games will vary there are however certain rules that will be the same no matter where you play and that you will have to follow if you want to play on a professionally run field.
In most cases the rules for each field will be posted or be available to all players who want to use the field If the rules are not followed then it could result in you being asked to leave and possibly banned from playing there again, this will depend on the field owners.
One of the most important rules is that you do not remove your mask while on the playing field. There is usually a section where you can remove a mask which may be referred to as a safety zone or neutral zone. This is where most players keep their gear bag and paint. Another rule will be when you are outside the neutral zone you must have a barrel condom on your gun at all times, this will prevent anyone from being shot if the gun were to discharge accidentally.
Another rule will be that before playing a game you will have to make sure your gun is not shooting too fast. Fields will have an area that you can check your gun before you enter the field to actually play a game. The speed of the gun will depend on where you are playing and the game rules.
As far as clothing is concerned you can wear anything you want to, but keep in mind that when you get hit by a paintball it will leave a mark and it is advisable to wear proper clothing before entering a field to play. You will have to wear a mask and have a barrel condom before playing, but the rest is entirely up to you.