Stand up straight with your back to a wall.
Place a tennis ball against the wall and lean your upper back onto the ball.
The ball should be between your spine and your shoulder blade on the side you would like to work.
Bring this arm across your chest in front of you, using your other arm to facilitate this movement.
Roll the ball around the area.
If you feel a particularly tender spot, hold this position leaning back onto the ball to place some pressure on the area until it releases.