Walk to the starting line and watch for a while, behind the starting line. Look at the way the track staff motions racers to pull into the water box, the signal to start your burnout (if you're unsure just wait for the other guy to start), and the way the starter motions cars to enter the timing lights (you may be motioned to wait for the previous cars to exit the track). Make sure to make note of where the timing lights are. I think just about everyone has driven past them on accident, but if you do, make sure you back all the way out and start over (this is a rule to make sure you're in a forward gear).
I would suggest not even trying to run hard your first time out. Just go through the motions to see what the whole process is like, then go from there as you feel comfortable.
Take a helmet as a minimum. Unless you have some painfully obvious safety issues, tech shouldn't be a problem. At a test n tune, tech usually consists of you handing the tech guy your filled out card and him going "ok" and waiving you on. Other than that, wear appropriate clothes (long pants, closed toe shoes, and a t shirt is fine). Unless you go faster than 11.50 you probably won't even get a second look.
Most importantly: Have fun!!! That's the whole point, right?