This is not meant to be demeaning to anyone out there, but if there's one piece of advice I can give it is this: Know Your Model.
What I mean is this. When you register your entries you will need to fill out forms that ask what kit(s) was used, what scale is the model, and what is the model called. After registering 188 models at our recent show, I can tell you that nothing is more frustrating for the people trying to get modelers through the line than having to play "10 questions" with an entrant about each of their models. This is particularly true when you are handed 8 forms for models and the only thing written on the forms are the modelers name and something like "camaro" or "t-bird" and nothing else. No scale, no kit manufacturers, no comments on aftermarket parts...nothing.
This is a bit of a rant and most people would think this is common sense, but you would be surprised.
If you can swing a mirrored base to display your car, do it. Mirrored bases do two things right off the bat. First, it tells everyone, including the judges, that you are proud of your entire model and have nothing to hide. Second, it adds to the "Wow Factor", which anyone will tell you certainly helps in getting consideration awards.
Good luck and enjoy the show!