Here's my addition to this topic......
1) You only get four runs so wasting the first one with the "I'll use the one to find the course" attitude is not good. Like Richard said, *know* the course before your first pass.
2) Don't let a mistake early in a run get you rattled. If you hit a cone at the first gate forget it and try to get the rest of the course right. IMO you can never *make up* for a mistake by pushing harder the rest of the run.
3) Watch, listen, and learn from those who are faster than you. Ask questions,

you'll be surprised how nice most of your fellow competators are. Well except a certain one who shall remain nameless right Kevin?
4) Catch a ride *every* chance you get.

A lot can be learned watching a fellow driver's technique at speed. Also ask others to ride with you because they can give you invaluable feedback on your run. The knowledge gained outweighs the performance lost due to the extra mass in the passenger seat.
5) Leave the car alone! It's impossible to learn to drive a car that you change every event. Learn the limits of your current setup before you decide to move on to *bigger and better*. Attend a driving school and learn *how* to go fast.
6) If you are convinced that your car can not go *any* faster

let someone else (an experienced driver who's beating you like a drum) take it on a fun run or two. 9 times out of 10 you'll find that the car is way more capable than you are *currently*. I'm sure the "Prez" will be more than happy to thrash your car any time and show you it *can* go faster. Also you will save you money because you're not dying to buy new *go fast* parts that are not yet needed.
7) HAVE FUN!!!!! This is *the* most important! Hang out, meet people, learn about car stuff, make new friends, and just have a good time. If you come to autocross just to drive 4 minutes then you are missing the best part. I know some take it more seriously, but I like to have fun. Sure winning is great, I ran two whole seasons and never won, but I had fun the whole time.