I havent read the other replied, but my suggestions:
Before you go: remove everything from your car (mats/glovebox stuff). Learn the track via youtube so you know which way to turn! Go to websites talking about apexing and heel-toe and try and learn driving basics. Learn the flags for your club (they can differ from club to club).
Bring: torque wrench, snacks/food (I like PB&J and chips), lawn chair, LOTS of water (stay hydrated, force fluids, pee before going on track
), decent tire pressure gauge (borrow a IR temp gauge if you can), painters tape (for your #'s), up to date helmet, camera, and shoes which have thin soles and fit snug.
Do: park near a shady spot, meet others (especially ones with the same car), have a good time, LISTEN to your instructor (You dont
know more than him/her), drive within your comfort level (7/10ths is just as much fun as 10/10ths IMO), WATCH your rear view mirrors for cars coming up (wave them by early on the straight), watch the corner workers. Dont use your ebrake when in the pits, just leave it in gear on a flat area.
Dont worry about upgrading your car for the first few events. The tires and brakes and fluids are all fine for a first-timer.
You're going to love it! Post pics later!