There are these pesky little particals in the air called dust. Make sure your car doesnt have a single one of these on it anywhere. Also check for fresh grass clippings if your in a field. Finally and most important buff that paint till you can read your watch in it.
Of course these apply if you want to win, but you should go to have fun, not win.
Make sure the windshield is clean, no spots. I got dinged for one rain drop. Check the keyhole for wax. Park your car where the most traffic is, if it is being judged by the public. Talk to people. Most people want to ask you about your car, but don't know how to start the conversation. You start it and they will remember your car when they vote. Wax in the weather stripping, get it out. Head lights should be clean. Clean aroung that license plate and door sills. No dust in the air condition ducts. Clean rims and inside the gas cap door. There is a lot to do but it depends on the type of show your going to. If is is judged by professional judges, then everything has got to be perfect. If it is a club show or sponsered by a car dealer etc. , most of it is eye appeal along with cleaning. Watch which class you in. I have a 98 Vette with mods, mainly chrome eng. parts, nothing fancy like high rise hoods etc. I was in a show by a club Sunday. My car is mostly stock with bolt on and I had a C-5 Zo6 Lincfelter (spell that wrong) chrome with a high rise hood Mag charger and NOS bottle in the back, none stock rims and gull wing doors etc, no way was he in a Modified Class. Total custom class. So watch what class they put you in. I have rambled on enough. Do the best you can with what you have and enjoy the shows and the other Corvette owners that your going to meet.