Originally Posted by ilovemyPhillip
If you get into a situation that he WONT stop, do a 1 reign stop. (take one reign, pull until his head reaches his shoulder, the hop off the pulled in side).
^^ Was going to mention the same thing. I've been using it with my OTTB - I ask once normally (lean back and pull lightly on the reins) and if he ignores that, pull his head around. It doesn't necessarily have to touch his shoulder, as he may not be that flexible yet, the point is to make him circle until he stops. Timing is everything! As soon as his feet are still, let the rein go.
Another important thing to remember is that you want him to soften as well, you don't want him leaning on the bit.
My boy has gotten to the point where he only does half a circle and then he stops, or on good days he will simply flex his head around and stop straight.