HOW: Stand with your back against a wall and form a wall angel. Your goal should be to try to keep your elbows and hands against the wall the entire time. If you are not able to, that is completely normal and it means you have some mobility to gain!
FEEL: You should the muscles in the front of your shoulder stretching as your raise your arms overhead.
COMPENSATION: Do not let your back arch, keep your core engaged the entire time. Try to keep your elbows and hands against the wall as you raise your hands up for as long as you can.