The biggest thing is to go into the experience with absolutely NO expectations.
Save ONE. Have fun.
From a basic "prep" point of view, inflate your tires to 10 PSI over the recommended prior to your runs.
Be sure to return them to normal before you are finished.
If you have the opportunity, ride with an experienced driver or an instructor. Work the course with an experienced driver.
Rule 1. Learn the course. Walk it as often as you can, but walk it as if you are in the driver seat. So, put about a foot between you and the gate to your left ( for driver side apexes) and about 5 feet on the right (for passenger side apexes).
Rule 2. When you get into the car, remember that "slower is faster". That's not to say cruise around at 10 MPH, but rather don't overdrive the car. LOTS and LOTS of tire squealing may amount to a lot of flash, but you are actually slowing down.
Rule 3. Take an instructor with you. If anything, they show you the course. By doing this, I am certain that you will drop 2+ seconds off of your first time in subsequent runs.
Finally, go out there with the attitude that you are all about learning and not about beating the other driver(s). If you do go out with the attitude that you will win outright (and you may - but doubtful), the you will quickly become discouraged. Focus not on the other guy's time, but on you own and use that as a measurement of your improvement.
Even 1/10th of a second is huge. On average, each tenth of a second = 2 car lengths. So, if you improve by 2 tenths, then you finished 4 car lengths above your previous run. That's pretty impressive!
So, do the math if on your second run you will be 3 or more seconds faster (which WILL happen).
Good luck! Have fun! and let us know how you do!!!