My pony doesn't handle going into start boxes.. crazy as he is and always has been an eventer and loves his xc but he just absolutely spazzes and starts rearing and running backwards - won't go near the box no matter what.
So as I have to get off him and lead him in, and once he's in he stands like an angel!
When they're counting down I just think about getting on and getting set to go and by the time i'm ready it's usually time to leave!
With my others I just think over the course and get rid of all negative thoughts, talk to the horses, and head off in a nice strong canter. :)