HOW: The goal of this exercise is to use your opposite arm as much as possible to facilitate improving the desired motion. Hold onto a stick or something light that is long enough to hold in both hands. You will have both palms facing up while holding the stick. Using your left arm, drive your right hand out to the side by rotating your shoulder as far as you feel comfortable with. Slowly return to the starting position and repeat, as you perform more reps you may increase your range of motion.
FEEL: In this example, you should feel your left arm doing most of the work and your right arm going for a ride. You should feel your right arm rotating out to the side. You may feel a stretch in the front of your shoulder and even into the biceps region.
COMPENSATION: Do not turn your upper body. Do not bend your wrist. Do not let your elbow move, try to strictly perform shoulder rotation. If it is uncomfortable, you can place a rolled up towel or pillow between your elbow and your body and this may help.