Lots of lateral work. Half pass, side pass, forequarter yield and hindquarter yield. Shoulder ins and haunches in are excellent for this.
Also increasing and decreasing the diameter of the circles.
Serpentine, figure 8s. There's so many.
I work at the beginning the folds, and as Dereck, I work the both side equally! That's really important! Be careful of not being too tough!
You should work the both sides equally! I begin with the side where he feels the most comfortable. It permits, at least at the beginning, to avoid his problem's side. We should avoid to fold them because at the beginning they're already contracted.