make sure you take EVERYTHING out of your car thats loose. (cd visor things, garage door openers, change, cell phone charges, etc. if they're not in your glove box or in your center console, take em out. i'd also remove your spare tire & anything else in the trunk.
(when i went to my first auto-x i didnt know any of this.. i only took out my subs & left everything else in my car. i spent 10 minutes taking all my **** out lol)
other than that, just have fun. my first run, i was SO NERVOUS. but each run after that i got super comeptitive because i wanted to keep beating my time.
out of 5 runs i ended up shaving 10 seconds off of my time
ALSO- i dont know about you but whenever i brake (regardless of circumstances) i always put in my clutch. this was a habit that i needed to break when i was auto-xing because it takes up too much time. when youre going around turns and corners and stuff, just brake with your brake pedal.
if there are slaloms (where you have to weave in and out of cones) the key is to keep your car from making big movements because that slows you down. try to stay as tight as possible and just lightly turn your steering wheel enough for you to avoid the cones.
hope that helps a little bit. i've only auto-x'd once but these are things that other experienced drivers told me my first time