I find that hitting against the wall is good with the caveat that you focus on the mechanics of your strokes and footwork and not so much pace or spin. Oftentimes, I'll rally against the wall and will wait for the ball to come back to be and end up hitting most of my shots around my ankles. What is the old adage: perfect practice makes perfect??? So move your feet and focus on hitting the ball in your "wheelhouse" each time. Also, try to videotape yourself hitting against the wall so you can see the mechanics of your shot.