STOP trying to stay still and hit the ball. This so-called technique is commonly known as setting-up. Instead of stalwartly standing still, run and hit the ball and let your body find its own balance. You CANNOT micro-manage your shots. Running and then stopping to hit the ball is contradictory to what you are attempting to accomplish when playing tennis. Your goal is to play tennis more automatically and instinctively. If you think coming to a screeching halt to hit a ball is more efficient for the body then I guess you would believe that a wide receiver should stop, stand still, catch the football then continue running? I don't think so!
This notion of stopping to hit a ball disrupts the flow and follow-through of your shots and makes balancing yourself that much more difficult. Players erroneously think that if you come to a complete stop and hit the ball, your balance will be better. But tennis is not a game that you are trying to balance yourself in one spot! You must move -- and move in many different directions quickly.
You should not try to stand perfectly still on your shots or when you are advancing to the net to hit a volley. This is another common myth that you should pay no attention to. When advancing to the net do not even think about stopping to hit the ball, just hit it and keep moving. Your body will work out the details. Remember, the wisdom of the body is smarter than you are. Stay out of its way!
What do the best in the world do? Simple. They hit and let their body move in whatever direction is necessary for any given shot. This is a much easier and much more efficient way for the body to perform.
COMPLICATED DECISION?
You can hit a tennis ball on the move the easy way, like the best in the world, or you can hit the ball the more difficult way by stopping and standing still. It's your choice.