The setup: Set a striped ground pole or cavalletti (with the striped pole on top if you have trouble finding the center of your fences) across the track of a large circle, about 60 feet in diameter. (As you feel more comfortable with this exercise, build the pole up to a crossrail or a small vertical.) Place a traffic cone just outside the track on the far side of the circle, opposite the pole or cavalletti.
What to do: Pick up a right lead canter on the circle. As you approach the cone, turn your eyes across the circle to the ground pole and keep them glued there. If you feel your horse wanting to follow your eyes and cut or fall in instead of staying on the circular track, keep your outside leg on him at the girth and shift both hands slightly to the outside to get him off his inside shoulder and onto his outside shoulder and haunch. Take your outside (left) hand about three inches away from his neck, for a leading or opening outside rein, and bring your inside (right) hand slightly across his crest in front of the withers - an indirect rein. If you feel him wanting to bulge or swing his haunches to the outside of the track - especially as he approaches the ground pole - bring your outside leg slightly back and on. As he canters over the pole, turn your eyes, look at the cone, and continue on.
When you feel comfortable with this exercise tracking right, do it tracking left. When you're comfortable looking ahead and keeping your horse straight on the circular track, you can add a second 60-foot circle, place the ground pole or cavalletti straight across the point where the arcs of the two circles touch, and practice the exercise in a figure-eight. Focus on meeting the ground pole or cavalletti straight (not at an angle) and ask for a simple or flying change of lead a stride or two after the jump, then change direction for the new circle.
From "Independent Eyes" in the March 2001 issue of Practical Horseman magazine. Discover Scott's simple exercises to solve lead-change problems in the September 2002 issue.