Do some figure eights, some serpentines, but remember to get him straight and slow him down before the change of direction. Half halt him to let him know something is coming. Then use your inside leg, supporting outside rein, inside rein to supple and create the new bend. Also if he's never done them, it is okay if he breaks to a walk through the turn. Depending on how many rides he has had, you can start asking him to move of leg a little. Half half on outside rein and use your inside leg to ask him to step over with his hind. One step is all you're looking for; do this at the walk. If he doesn't step over, tickle him with the whip and when he does immediately praise him.
Yup, I'm just gonna go out and say it, I am a complete CA freak. I love his training program. I've fixed a lot of issues with horses that I had problems with.