Any tennis player is only as good as his footwork. Solid strokes are essential, but they will do you no good unless you can get into good position to hit the ball.
A secret to winning footwork is to keep your feet moving. Never stand flat-footed on the court.
Stay on the balls of your feet and anticipate your next shot as soon as you can. Don't stop to admire an unusually crisp shot of your own or the reactions of your opponent. Stay in motion and get ready for your next shot.
No less a player than Arthur Ashe, the United States Davis Cup captain, used to write notes to himself with an admonition to keep his feet moving. He'd leave the notes on the sideline where he'd see them between games.
That isn't a bad idea, either.