Move shoulders forward, then up, then up, then back while squeezing the shoulder blades together, then press them down towards the ground in a circular manner. Repeat in the opposite direction.
Bent forward (back straight) and arm dangling towards the ground, gently swing the arm in a pendulum arc. Repeat in the opposite direction.
Leaning into a wall with both hands placed on it directly in front of you, and keeping the arms straight, move the shoulders forward and back using the movement of the shoulder blades. Focus on spreading them, then squeezing them together over the spine.