Think about leading with your hips/pelvis. Let the horse “pull” you forward with him (later you can work on being in better balance with him.) Think about growing your legs long, like you were standing on them. Drop your heels down when the horse drops down- don’t pull your heels up. Start with a very small canter. Visualize those WP riders who don’t move a bit (OK, their horses don’t move either but just try the visualization).
These things worked for me.