Its very name is confusing, and really a misnomer. It is actually a drive, not a volley at all. It is arising bounce drive played just as the ball starts to rise from the ground, and should be hit with the grip, footwork, backswing, and complete stroke production of the drive-forehand or backhand. Except, of course, the ball can’t be taken waist-high. The real secret in hitting a half-volley lies in bending the knees, so that you crouch over the ball, leaning into the shot and following through to the end of your swing with a flat racquet face and a stiff wrist.
The common error most players commit is standing up straight and shovelling or blocking the ball, instead of following through and making a real stroke. The half-volley should be played only when you are forced to do so, because you’ ve been caught with a shot at your feet. It should not be deliberately chosen. Your better choice, if you are in the back court, is to move back and let the ball rise to your waist before you play it. If you are in mid-court or closer to the net, move in and play a low volley.
Since the half-volley is more or less a desperation shot made under pressure, play it for attack, not defence. Bit it firmly, decisively, and fairly hard, moving in with your shot as you make it. If you fall away from the ball, or attempt to half-volley it while moving backward, you will balloon your shot far out or up. If you always regard the shot arising bounce drive, played at the earliest possible moment, you can at times use a half-volley as an advancing shot to go to the net behind, but it should only be done if your opponent is far out of court and you are attempting to hurry him to the limit. It is dangerous but, if successful, very effective.
There is no shot in tennis that requires the perfect split-second timing that the half-volley does. Above all, it demands perfect vision, with the eye never leaving the ball for even an instant. It is fun to play, but its likely percentage of error is so high that it should be used only when there is no other possible shot.