Lots of hand walking around the show grounds and warming up for a while before hand!
I'm a list kind of person. So about 2 days before the show I create a list of everything I need. Bridle, halter, show coat, etc... then I look at the list and clean the things I need to bring. As well as clean the horse. Then, as I load everything into the truck/trailer, I check or cross off the things that are packed.