To make sure you are quick at returning volleys, ensure you use the same grip for both forehand and backhand volleys. The grip required is the "chopper" grip. The time saved changing grips helps you concentrate on reacting to the ball as being at the net, you only have half the time to react. This grip will also help you with serving and volleying, as well as giving you a much better degree of control for those awkward net shots.

Bonus tip: If you have half the time to react, that means so does your opponent. The only difference is that they don't have the luxury of using the same grip from the baseline!