Hissing and a seat change. Jake is 20 now and he doesn't like to run as hard in the arena anymore, so every once in a while I'll use an over-under about 2-3 times per run. He has big strides so he learned that by the time he got to full speed I was pulling him up. Every now and again he likes to show me how fast he will go, but its getting rarer and rarer. I don't mind to much.
I also make sure I try to not make him sou about it. I make extra sure to never yank on his mouth once we pas the finish line, and let him slow down slowly so he isn't fearful about being slammed on after going a few strides. I also try to limit practicing to 3-6 times a month during show season, and only running the pattern hard at shows or once a month if I am not showing. He gets burned out, so I do my best to make sure not to. So during the off season I mostly do english. If I want to show, I'll freshin him up a bit a week before. He hasn't done any pattern work in over 4 months now. I think he enjoys the break.
But out on trail he loves kicking it up to full speed, I pretty much takes a slight seat change and calf pressure and he is gone. =)