How to: Get on all fours with wrists directly beneath your shoulders and hips over your knees, then sit back a little so hips are behind knees and wrists are just in front of your shoulders. Gently clasp 1 hand behind your neck (not your head), while keeping the other arm locked out at the elbow, with shoulder packed. Touch elbow to elbow, then externally rotate away as far as you can go, looking in the direction your rotating. Pause for 1 full breath at your end range of motion before repeating.
Compensations: Watch for bending of elbow of the plant arm, clasping your head and pulling downward. Watch for holding of breath and moving from your hips.