HOW: Sit next to a table with your affected arm resting on the table. Make sure there is little friction on the table, you can easily place a towel, shirt, or some other object on the towel to make it slide easier. Your goal is to keep your arm and shoulder relaxed on the table, and then try your best to bring your arm away from your body. Reach as far out as you can in a diagonal direction, so not out in front of you or to the side of you, but in-between those two directions. Hold for a few seconds during the stretch, then return back to the starting position. Repeat.
FEEL: You should feel a slightly uncomfortable stretch at the end of your range. This is common and the goal of this exercise is to feel that little bit of discomfort so don't be alarmed.
COMPENSATION: Don't lift your arm off the table. Simply slide it along the table.