The following article is the SINGLE MOST HELPFUL article for me to improve my tennis game. Hope this can help some of the tennis players out there. 

The Unit Turn - Your Tennis Foundation

A favorite question to our juniors in the afternoon classes goes as follows, "OK, so you are in the ready position with the knees bent, racquet held lightly in front of you, intently watching your opponent as they are about to hit. Now, just what exactly is it that you are ready to do?"

The answer goes to the heart of the game and tells a lot about your own feel for tennis. Often heard responses include, "Get the racquet back," or "Start moving my feet to the ball," or "Take a quick skipping step to the ball." In some ways each answer might apply for certain situations, but the simplest move, the most efficient response to the situation and the correct answer to the question is, "I am ready to turn."

Nothing more, nothing less, just turn. The turn must be as soon as possible. The turn should not disturb your balance or your vision, and it should be quick but equally subtle. This simple turn, aka the "unit turn," rotates the hips and shoulders as one unit, and puts you immediately into either a running or hitting position. Running, because your hips are now facing the direction you will move, and hitting because your shoulders are lined up for an efficient swing.

A few comments about leverage and power. Tennis is a game of optimal power, not maximum power. That is, it's great to crack the ball, but first and foremost you must control the ball. This is what the unit turn gives you and why I've described it as the foundation of your game. Teaching pros often say something like, "You should feel your body swinging the arm and racquet. You should never feel like your arm swings the racquet." In order for your body to swing the arm, you needs both linear and rotational momentum . When I've completed my unit turn, my weight is on my back foot and my hips and shoulders are turned sideways to the net and the on-coming ball. Therefore, I am poised to step and turn back into the hit, momentum going foreward with the feet and then rotational momentum with the hips and shoulders. Controllable leverage, controllable power, effortless tennis.

When studying professional examples, Jimmy Connors had as simple a unit turn as any modern player. Efficient, because he made that same turn for all forehands and all backhands. Further, because his style was to play the ball very early, his turn was as quick as any ever seen (Agassi may actually be taking this early preparation to a new level but that is another story). The simple and quick unit turn enables early preparation, ensures a good jump on the ball when you have to move, and adequate body rotation into the shot because of your initial turn to prepare for the ball.

In the photo sequence I am moving from a ready hop into either the forehand or backhand. As you study the pictures note the following elements, which will be your own keys to perfecting this move as you practice it again and again and again.

Forehand Unit Turn

• The posture is unchanged from waiting to the turn.
• The hips and shoulders are turned but the eyes are forward on the incoming ball.
• The arms and elbows are relaxed throughout.
• The turn of the shoulders and hips automatically takes the racquet back.
• When turn is complete my weight is on the back foot.

The elements for the backhand unit turn are the same as the forehand .