If you've seen the backhand volleys of Tony Roche, Ken Rosewall, John McEnroe, Pat Cash, Stefan Edberg, Pete Sampras and Pat Rafter, you'll know how effective this shot can be. Of today's players, Roger Federer and Tim Henman are its best exponents.
Of the above players, Roche is considered by most to have had the best backhand volley of all time. What made his shot so great were accuracy and penetration; he got an unbelievable amount of "bite" on the ball, which made it very difficult to hit passing shots against him.
For best results, use a Continental grip, or as close to a Continental grip as you feel comfortable with. The further you move away from a Continental, the more you'll need to change your grip while you're at the net.
From the ready position, in which your weight is on the balls of your feet with the racket held out in front of your body, turn to the left from your waist.
After this initial move, step across and forwards with your right foot, while preparing your racket for the volley by taking it back (with the weight of your racket mainly in your left hand) no further than your right shoulder.
With the racket in this position; i.e., ready to move it forward to make contact with the ball, your wrist should be cocked with your racket head above the wrist. Your elbow should be a comfortable distance in front of you to prevent any chance of hitting the ball late.
The racket face should be open, with the angle of openness determined by the height at which you anticipate making contact. Your racket head should be at a point slighly higher than contact height. The lower the volley, the more open the racket face.
It should also be noted here that you must bend your knees - not your lower back - to get down for low volleys. In fact, your actual stroke should be virtually identical for every backhand volley, no matter from which height you hit it. In preparation to start your forward motion, the full face of your racket should be ready to meet the ball square on.
Whatever you do, don't have the racket head end of your racket pointing back behind you. This will prevent you from getting your racket to travel in a straight line forwards, creating timing and accuracy problems.
As you move your racket toward the ball, your elbow - from a comfortably bent position - should straighten slightly. Your wrist should stay firm at all times, and your left arm should travel in the opposite direction of your racket arm. You should feel your shoulder blades squeeze together as you spread your arms in opposite directions while playing the stroke. This will give you balance in the same way tight-rope walkers spread their arms to maintain balance.
If you're looking to hit a backhand volley like a pro, you should aim to hit the ball no more than a few inches over the net, but with enough pace so that your volley lands deep.
Practicing your backhand volley on a wall or backboard will lead to rapid improvement.
Draw a line on the wall (the height of a net is 3 feet in the middle and 3'6" at the side), and practice hitting at a height no more than 6 inches above the line. Vary your distance from the wall. If you can hit a number of consecutive backhand volleys within a six inch range of the height of the line, while standing 3 or 4 meters from the wall, you've got a decent backhand volley.
Because practicing your backhand volley against a wall will quickly expose any technical weaknesses, this method of developing your stroke is very good as, with thought, the weaknesses become self correcting.
I would definitely recommend that all players learn to hit a backhand volley with one hand. Two hands on the backhand volley limit your reach too severely. You can get away with it in doubles, but, in singles, your reach limitations can be exposed too easily.
For very advanced players, practice your backhand volley while gripping the racket with your thumb and three fingers only. Do this non-stop against a wall for 15 mins - or longer - each day, and then enjoy the benefits of holding the racket with your full grip. What this will do is fast track your progress by building your muscle memory more quickly than normal.