Hitting the Forehand Volley Succesfully

The very best tennis volleys in the world are not a full swing, but simply a firm block of the ball.   First off, you need to be patient and wait for the ball to get to your side, otherwise you'll be chasing it forward, rather than blocking it firmly.  If you wait for the ball to get near you and then you'll hit it by locking your wrist and your arm, the trunk of the body connects to the impact, generating more power than a loose and swinging arm.

On the forehand side, make sure your elbow is tucked in to the front of your body.   A floating elbow will give you plenty of errors and more difficulty controlling the shot.  It is good to hit across the ball, this meaning that the butt of the racquet moves a couple of inches to your left, as if you were hitting the palm of your other hand with it.  

Remember that the main factor for power is not swinging at the tennis ball, but the weight you connect to the volley block.   The placement of your volley is totally dependent on the angle of your racquet, not on the direction of your stroke.   Volleying a hard passing shot, after finding the ball path with your racquet, the hand may go on a very short motion, tightening up when you meet the ball.   On a high and slow volley you would need more of a follow through, but always tightening the grip and arm muscles when you meet the tennis ball.