What is the best stretch exercise for shoulders?

For shoulders, reach one arm across the body, then use your other arm to push your elbow towards the opposite shoulder (i.e. reach your left arm towards the right side of your body, then using your right arm, push your left elbow towards your right shoulder). Start the stretch slow and do not push too hard. You can also reach behind your head, with your hand touching your spine and use your other arm to push your elbow down and towards your midline. As a final stretch, while standing, bend at the waist and let your upper half hang as loosely as you can. Slowly rise back up, focusing on keeping your upper body as loose as possible while you do so, straightening one vertebrae at a time.