Starting about 2 metres away from the front wall and face the side wall and stand close to it.
start to hit some volleys to yourself (forehands if you are right-handed, backhands if you are left-handed).
Keep you writs firm and make the shoulder do the work. Hit about five and start to slowly move away from the sidewall but parallel with the front wall.
When you get near the left sidewall wall, move a little further away from the front wall and then start to move forward again.
All this time you should be volleying the ball.
If you make a mistake, go back to the beginning.
Your objective is to make it past the short line, so about mid court.
Advanced players should be able to make it all the wall to the back wall.
This is a touch exercise, both mentally and for your shoulders.
Give yourself 5 minutes break by doing something else and then try it on the other side.
Keep a not of how many volleys you do without a mistake.