HOW: Begin with your forearms against the wall while keeping your body in line (feet up to shoulders). Allow the scapula to sag then push the scapula away from you by pushing your chest away from the wall. This will cause rounding of the mid-back. Return back to starting position and repeat. This motion should be coming from the shoulder blades.
FEEL: The Shoulder muscles working.
COMPENSATION: Don't bob your head as you perform this, keep your head stationary, the motion should be coming from your shoulder blade.