Definitely give your horse a trim a few days before the show (bridle path, whiskers, ears, feet). Day before the show, give your horse a good bath and put on a mane tamer or slinky for the night (if you can). If it is expected to band the mane, do so before putting on the mane tamer. Most shows around here (including 4H, larger Open Shows, and even breed shows) have fewer and fewer horses with banded manes, but it may be more expected in your area. The day of the show, make sure the horse is clean (I wipe a damp cloth over the horse to remove any fine dirt or dust that is on the coat, mane and tail are well groomed and shaving-free, wipe out the nose, and wipe off and paint the hooves. I also spray on a "shine" product to the body (excluding the saddle area) and the mane and tail. I use Pepi Coat Conditioner to add the shine.