Standing with feet shoulder width apart, drop your bottom to a 90 degree angle. Hold the medicine ball either at your chest or closer to your waist, whatever feels more comfortable. Next explode through the feet and jump in the air. It is key to keep your back straight, and not to hunch forward.
For more emphasis on the glutes, drop your bottom as far down as you can or "in the bucket". For more work on the quads, "hack" the squat motions so that you are dropping to less than a 90 degree angle