my first show i went there with no paint job (just kit and trunk conversion) and no interior work i took 4th place in the under construction (no trophy though for 4th)

1- my rims were clean (took off all four the night b4 and cleaned each one font and back), while they are off clean brake pads, rotors anything that can be seen thru your rims
2-make sure anythig you showing is fixed (body kits, wings, hood, etc.) one little mistake is all you need to lose
3-music/lights make sure whateva you bring is something a crowd of people wouldnt mind listening to (no country music in a hip hop crowd) lights/strobes keep the color schemes matching your ride and have an extra battery.
4-be social to people cuz you will be asked the same questions 100's of times or get a board made so people can just read your mods if you dont want to answer it 100's of times

everything else was covered already... BTW its best to wax the car when you get there (just get there early) however wash it the night b4 and no eating in/near the car....