There are many facets to hitting a solid ground stroke, but if you key in on four simple areas your shots will improve.
Movement is number one; tennis is a sport that requires quick feet. The stroke is dependent on the fact that you are in the right spot to hit the ball. Moving the feet side to side in between shots is a must; this will have you ready to react to the ball faster. When approaching your shot try to use quick small steps, except when all out running is needed.
Preparation is number two. Whether you have a straight back or loop back swing, early preparation is the key to a smooth, non-hurried swing. The straight back players should use the guideline that when your opponent’s shot lands on your side of the court the racquet should already be back. Unlike the loop back swing, the straight back is not in continual motion, but in two halves, back early-wait-hit. The loop should be started early enough so that the racquet head is below the height of the ball before the forward swing.
Number three will be balance. If you go back to number one, and have quick small steps, that will lead you to a balanced shot. When hitting, you do not want to be stretched or leaning too far forward, but more erect. This allows for a balanced weight transfer into your shot. Never transfer all the weight, only half, leaving the other half on the back leg, at contact. Remember, bend the knees!
The last will always be your follow through. No shot is ever complete without a complete follow through over the shoulder. Just trust your swing. There is an opposite factor here, (tennis has many of them) which is, the shorter the follow through the higher your shot will go, the longer the follow through the lower it will stay. You need to keep the ball on the strings as long as possible to generate your control factor, topspin or backspin.
For more tips and my book Winning Tennis Strokes, go to http://onlinetennistraining.com.
Good luck ... have fun!