1. When correcting technique on volleys, it's almost always taking away a movement, rather than adding one. "Less is more" prevails for this simple stroke. Because we are normally at the net when using our volleys, time is at a premium. The volley needs to be efficient in order to maximize time needed to prepare and recover back to a ready position.
2. The strings should follow the same path after contact as the ball traveled on its way to the strings. Often you'll hear the racquet hit the ground after striking a low volley. This is not necessary and really shouldn't happen to optimize your volley technique.
One good exercise to practice this technique is to volley a ball against a wall repeatedly. This gives you little time and will help force you to have an efficient stroke. Set goals like 10 in a row, and then higher and higher as you progress.
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