Holding a cup of water when you practice your volleys can help you achieve better balance.

If you feel like you lean to one side when you're volleying, holding a cup of water in your non-dominant hand can remind you to keep your upper and lower body quiet so you don't spill a drop. By using a small cup of water, you get instant feedback on any unwanted body movement.

Kathy Woods is the director of tennis at the USTA National Campus at Lake Nona in Orlando, Fla.