there is a auto-x forum here on FF, there is some FAQs and first time pointers, so i wont list them all but:
have fun, people are very firendly so talk to them and ask for help. and ride along with experienced drivers to learn from them.
and pump up the pressure in your tires. i'd start at around 45 #s
for auto-x: '04 Liquid Grey ZX3
for street: '02 Infrared SVT