Load your magazines for rapid fire the night before, and mark them with a paint marker or masking tape so you don't get them mixed up. Remember, you start rapids with the two round magazine and reload with eight. And about rapid fire -
slow down. A lot of folks, myself included, think "rapid fire" means you've gotta rush. Yes, there is a time limit, but if you calm down and relax, you'll have plenty of time for the string.
In general, just try to keep your ammo, magazines, and other odds and ends organized and easy to find. I keep all my slow fire ammo in plastic MTM boxes (marked for whatever yard line/position they're to be shot at), and have my rapid fire ammo for 200 loaded the night before. I put my offhand ammo in my jacket pocket holder the night before, and have one 20 round sleeve of ammo dedicated for sighters only.
Don't get too hung up on buying top shelf gear; I used my pistol range bag to haul my stuff around in the first couple of matches, a beach towel for a shooting mat, my work jacket for a shooting coat, and an old welding glove for a shooting mitt. Plus if you get hooked into this - and you will
- you'll probably find good deals on nice used gear from other shooters who've done this for several years and are upgrading their old stuff.
I like to take a little cooler with me with some snacks and bottled water to get me through the day, especially the water, since cool, non-humid days aren't exactly well known in Georgia during the summer.
Pay extra attention if/when you're scoring. When you're scoring for another shooter, you are temporarily a match official and you may be called on to help settle a dispute on the line or in the pits on your shooter's target. Pay extra attention during your shooter's rapid fire strings to be sure he/she got all their shots off. Keep count during their slow fire strings so you don't miss a shot.
Same goes in the pits (if you're shooting somewhere that has pits). The pits were the most confusing and nerve wracking thing for me the first time I shot full course. You get what you give for pit service, so try to be smooth and fast.
And above all else, have fun! A clinic type thing is the best bet for a new shooter, since attitudes will likely be pretty laid back and relaxed.