You, your car that's in good running order...i.e. no leaks, good tires, etc. If you have a stereo box and it's not bolted down it has to be removed. They have loaner helmets or if you bring one make sure it's DOT and Snell M95 or newer. Cash obviously to pay for entry fees, I believe it's $30 or $35 for non-members that show up. No forms except the insurance waiver and the entry form you fill out at the event.
If you get there and are lost just find someone that looks like they know what's going on and ask, everyone there is very friendly and always help pointing out where to go for the noobs.