Have a good breakfast, we have bbq for lunch. Also a few of the regulars go to dinner after at a local steak place, you're welcome to come along - we start eating about 6pm and finish by 8pm so you'll be getting home a bit later but it's totally your call. That goes for anyone really, any club members come along and budget $50 for food and a drink or two
Bring a hat and sunscreen if you're prone to sunburn. Other than that - just turn up and don't be afraid to ask questions if you aren't sure what to do. It's very straightforward in the morning though; get there with time to spare, find a spot for your stuff, empty the car out and put the wheels on you want to use, then join the line for scruitineering and sign on (license check etc, bring club membership card), then go back to your spot and wait for drivers brief.
EDIT: Don't forget to bring the correct clothing for driving (long sleeves and enclosed shoes etc as in the supp regs)