Player Balance
A great youtube video on balance to share:
http://www.youtube.com/watch?v=rZl7Iysd2pk&feature=mh_lolz&list=PL87E272025A70B2D4

And the following write up:

There are 3 primary components of good balance: Feet, hands, and head.
First, lets cover the feet. Players should move and set-up to hit in a lower playing height, rather than upright in their standing height. To find your playing height, bend your knees to the point that you can no longer see your shoelaces.

There are also 2 ways to be on balance with your feet: Static balance and dynamic balance. Static balance is being on balance and stable while hitting. To develop this basic skill, play mini tennis and hold a cup of water, trying not to spill a drop.

As players progress they often have dynamic balance, meaning that although they may be in the air while hitting, they still land on balance after the shot. This occurs due to the sheer velocity of the swing generated through the legs, body rotation and arm speed. Some examples of dynamic balance:

First, on short high balls, players will push off their front foot and land on their front foot.

Second, on wide and deep balls, players will often load on their outside foot and push off to land facing in the direction they will have to recover.

Third, on wide balls to the two-handed backhand, occurs when players have time to load on both legs. They push off explosively, rotating and landing on both feet, helping them to quickly face and recover in the right direction.

Finally, players today also often take an extra step forwards after contacting the ball. I call this the follow-through step. It happens naturally when players set up early and lean in towards their target. One of the hotly debated questions on this topic is whether or not to teach these various footwork patterns. My feeling is to observe the player over time and help them to evolve their own set of athletic skills.

The second balance issue deals with the non-racquet hand. Often overlooked, the left hand for a right-handed player plays a huge role. It may be to line up a forehand. Or, during the contact and release phases of the slice backhand, the non-racquet hand is an important part of overall good balance.

The third and final balance issue to discuss is the head. The concept of keeping your head as still as possible while hitting a tennis ball is quite simple. Try bobbing your head up and down the next time you are playing, and youll quickly understand. The more your head moves, the harder it is for your eyes to stay focused.
http://www.oncourtoffcourt.com