HOW: Get bands set-up in front of you anchored to a wall if possible. You can vary the anchor position depending on if you want more resistance with shoulder flexion (lower anchor point) or shoulder extension (higher anchor point). Note that a lower anchor point will make this exercise more challenging and easier to compensate once the hands are positioned overhead.
FEEL: Start out by driving your hands back towards your back pockets and squeezing your shoulder blades together. Think of pinching a pencil between your shoulder blades. While maintaining your hands in-line with your ears - raise your arms up overhead as far as you feel comfortable with. Pause for a second at the top followed by bringing your hands back down and returning to starting position. Now try initiating the snow angel by bringing your hands back overhead first and going through the motions backwards.
COMPENSATION: Be sure to not shrug your shoulders up towards your ears, excessively arch your back, or lean back.