My secret for a show ready horse is having a healthy, happy, fit athlete!!
The horse should be conditioned properly for the work that is going to be asked of him - this means training for the next season starts a few weeks after the end of "last season". The horse should have a good feeding program high in fat and with adequate protien, calories, minerals and vitamins to allow him to have strong muscles and hooves and a shiny coat. The horse should also be treated like a horse, turned out in a group and in a large area to run around. It is so much easier to train a happy, healthy, mentally well balanced horse! And they stay so much more sound.
Grooming at the show is of course important, but the thing that will make your horse stand out from all the other immaculately groomed animals is his overall health and attitude towards work and showing! My horse can't wait to hop in the trailer to see what kind of adventure we are going on =)
They say money doesn't buy happiness -- well happiness doesn't buy horses!