I did my first AutoX 2 weeks ago. All the advice here is excellent, I also suggest bringing sunscreen since you'll be outside all day, and possibly a lawn chair for watching others.

As for driving, I don't know how your traction control works, but you'll definately do better without it. And when driving, don't hold back, make sure you're pushing your tires to the limit. If they aren't screeching, go faster. My first couple of runs I was driving like I would in a neighborhood, after I got out of that mindset my times were much better.