Stick to factory PSI for your tyres. Dont overfill, as the air will become dense as the heat builds up obviously.
Ask a mate to take his car as well, even if not used for track. Best place to store fuel cans etc, as you dont want to leave them laying around for obvious reasons, and you dont want to take them in the car for obvious reasons also.
Just like Paul said, enjoy it. Ive been a few times now, twice with the Impreza when I had it and all I did was focus on building on my ability. Bettering myself as I went round, and taking enough notice of others to avoid a crash but not enough notice to let them become a factor of the speed I am doing.
ENJOY!