How's your drop shot? Are you hitting it too deep and giving your opponent an open invitation to the net? Or are you being too gentle and hitting it into the net?
The best way to master the drop shot is practice, and here are a few exercises to help. Do these in a progression.
Toss a ball about a foot into the air and hit it straight up with backspin. Your racket should travel in a semicircular path, like making a smile in the air. Continue to hit the ball in the air with this stroke, almost like your are juggling it with your racket.
Now, toss the ball up, let it bounce, and hit it forward on your side of the court with backspin. The objective is to have the ball bounce and come back toward you.
Lastly, stand near midcourt, drop a ball, and hit it over the net with...say it with me...backspin. You want the shot to land about 3 to 4 feet past the net, and when it bounces it should come back toward you.
You know you've got a good drop shot when it dies before it gets out of your opponent's service box.