Randy..... shows and classes at each show will vary depending on how many cars are expected to show up, what classes the show sponsor has judges for and whether the show has been registered as a NCCC show (for points accumulation for the owner/club). Most shows set up by NCCC Corvette Clubs are sanctioned, but not necessarily. I have judged a number of shows over the years and these are the breaks as I remember them. I'm sure if I miss something, someone will pipe in and correct me.
The general breakdown of shows:
Concours: usually broken down into classes C1, C2, ...etc.
In the class the cars must be as close to factory perfect as possible. And I mean PERFECT! EVERYTHING must be as delivered from the factory, even so much as having the owners manual in the proper place. No sunglasses, papers, dirt, dog hairs,...... NOTHING. Even a smudge on the windshield is cause for points deductions. Separate judges (if possible) will judge the Exterior, Interior and engine bay separately. points taken off and totaled up from all the judges.
Mod's: these classes can vary somewhat and I'm not sure of the exact number of mod's before the classes change. Mod's can be as simple as a color change, new rims, aftermarket radio, ...etc. Ext, int and engine bay here again too.
Wash and Show: Basically clear'er up and hope for the best. generally it's exterior and interior only as these cars are more often daily drivers.
People's Choice, Celebrity Choice: the fickle choice of the judges or public. Just for fun.
There are often more breakdowns than this depending on the size of the show. Also not unusual to see breaks within the generation (i.e. C3's), Sometimes if there are enough cars showing there will be a 68-72 break, 73-77 and 78-82. Sometimes you're up against all 68-82 C3's.
The point system starts at 100 points. When you arrive at a sanctioned show you will have your car "tech'd" in. Points will be taken off for (ex: horn doesn't work, or a tail light is out, ...etc). Then another judge will classify your car as I listed above. You have the choice of telling them what class you want to be judged in. Do understand that show judging is and can be very subjective especially in the Wash and Show and Peoples Choice categories. Concours levels are more technically precise but still it's people judging cars. Club preference is another "subjective" issue. And you will find that many of the people showing their cars are VERY passionate about them and their condition. It's their hobby and sometimes they are not happy about getting points taken off.
Also you will kill of an entire day showing your car in sanctioed events. usually the gate opens at 7:00ish. Rags down at 11:00a and judging begins. Depending again on the size of the show it might not be until 3-4:00pm before results are anounced.
If you've never done a show before I would recommend a Wash and Show category first. Learn what judges are looking for, see what other owners are doing and decide how passionate you want to be about it.
Good Luck............. nut