I've worked out a routine this summer where I can get to a handball court for about an hour before I go to work on days when I don't have a chance to play real tennis. Usually I just stand back about 35 feet and try to hit about 50 forehands, 50 backhands, etc. I also practice volleys from about 6 to 10 feet out - got that suggestion here. I don't like hitting serves against the wall. They come back at me too fast. It disrupts my rhythm. What else can I do to improve my game, make the time more interesting?