Here is the classroom material if you want to start reading it. We cover all the needed material in the class, but some find it helpfull to have already read it.
http://msf-usa.org/CurriculumMaterials/BRC_Handbook_Vs71_noprint.pdf
You need over the ankle footwear for the class. Ideally they should be leather with rubber sole. Motorcycle specific would be better, but hey there is that budget deal again. Very large heavy boots can interfere with getting used to the controls for a newer rider. You want something that covers the laces if possible. Whatever you decide to use, you want them to be broken in. If you show up with brand new boots you never have worn, it is not going to be a good weekend. Get used to those boots!
Something like these work danged good!
If not using a full face helmet (or you are using our supplied helmet) you will need eye protection on the range. Plastic lens sunglasses are suitable for the range exercises.
You will need gloves (full fingered). Leather, motorcycle specific is best.
Long sleeves are required. Bring a couple of long sleeve shirts. A jacket is best but even a ventilated one can get very hot on the range at slow speeds. A long sleeve shirt is acceptable on the range, denim would be better, bring a jacket as well.
If you have some light rain gear, bring it. If it rains we still ride. If you don't have any, consider buying a cheap one at wall mart or somewhere. It won't last in street riding, but even a cheap $10 suit will work on the range. I use frog togs at the range myself.
If you have access to a bicycle, ride it and work on your slow speed balance, looking in the direction you want to go. Keep your eyes level with the terrain, don't look done at the pedals, ground, or controls. Practice turns and turning your head in the direction you want to go. Looking for the target/exit to the corner but not looking down.
Work out your left hand with something to improve your grip. Squeezing a ball or better yet, there are some exercise devices made for it. There is a lot of clutch use and I see a lot of left hand fatigue in most riders.
Hydrate your body well for a few days prior to the class.
Get some good rest the day or two days before. Again I see quite a bit of fatigue on the range and it impairs the performance. If you want to go out and see OKC night life, and play, plan on staying an extra day and do it AFTER the class is over.