The best way to improve your tennis game is undoubtedly to play a lot and train a lot and get a good coach or playing partner that can keep you on your toes. This is an active approach. But you can also improve your game in a passive, comfortable way, by studying the greats playing or practicing. The key is not to just watch them hit the shots but study them. There are plenty of great close-up, court-view videos that can get you an idea of the technique of the top players. Just go on Youtube and search for them.
Take a look at the video above. Look how effortlessly Roger Federer hits the ball, how relaxed his movement his, how he moves his feet all the time, but not using big strides but very small steps. Just by watching a player like Federer train can give you so much inspiration and ideas to bring to your own game the next time you hit the court.