In your undersaddles the judge is looking for a nice forward (not fast, but in front of your leg and ready to move up) long and low "floaty" gait (not too much knee action), responsive and pleasant horse. Something that would be nice to take on a hack out in the country. It's judged largely on the quality of your horse's gaits, so do NOT hold him back like you would in pleasure class!! Some rider from the paint circuit came to our show, made her horse do the little peanut pusher jog, and barely moved at the canter, and then got mad her horse didn't place. Some of the horses I ride I keep more on the bit, some I let them go a little, but I always keep contact on their mouth. I usually get off their back a little at the canter so they can really use their body. You want a nice smooth transition that's not too hurried but easy to get (use a crop discretely if you need one). The order will probably be some variation of :walk, trot, walk, canter, walk, reverse, trot, walk, canter, walk, line up. Your horse will lose points for fighting the bit (toss their head), pinning ears, swishing tails, going to fast or too slow, picking up the wrong lead, etc. Don't stay on the rail if you don't have to do! Try to stay spaced out and don't let your horse get hidden from the judge by another horse. And of course, make sure your horse is turned out nicely! Bathed, pulled mane, clean tack, etc.