Guns are chronographed with 0.25g BB's. If you have a common gun we may have mags ready, but it is best to bring an empty mag to the chronograph station if you have something unusual.
Charge all your gun batteries and radios the night before, bring plenty of water, take a crap in the morning, eat a big breakfast, dress in layers, and make sure you have similar-toned dark or light clothing to fit onto one of the teams. Make sure you've read the rules in advance and have all the required equipment.
This page has all the info you need to know to come play at the field: http://www.thewarzon.../Open_play.html