Honestly? Everything... Are you going bonnet up or keeping it shut? If up, make sure you do a good job of cleaning it up, make sure all your fluid levels are topped up too, makes it look a bit more finished... Maybe PM Mr Turbo (Rob) and ask him as he did something similar a few weeks ago for a show and won a trophy, said it was all elbow grease but well worth the effort... Paint wise, a good clean and polish, and touch up any stone chips in the front bumper... can't really think of anything else, I've never shown a car before so that is what I would do... Good Luck!! And have fun with it!! Jack