Would you like a practice partner who's always available, always returns the ball, and never criticizes a poor shot?A backboard or wall is the answer. The best way to use a backboard or wall to groove your strokes is to stand well back and simulate real play.
Remember, the net is 39 feet away from the baseline on a tennis court. By standing well back, you can hit the ball after one bounce, just as you would in an actual match.
Practice hitting both forehands and backhands, first one and then the other. Angle some of your shots so you have to run to reach the ball.
Whatever you do, don't get sloppy. Use your best form on each shot. Watch the ball, get your racket back early, and follow through fully. Otherwise you'll just develop poor habits at the backboard that will yield poor results on the court.