"This is a nice one for the desk. Take your right arm straight up overhead. Bend at the elbow so the forearm lies across the top of the head (do the best you can). Take the left hand and gently pull the right elbow for more stretch. Try to extend the right elbow up towards the ceiling. When you breathe deeply notice how the ‘shoulder stretch’ effects all the way down to the hips. Someday the arm will come behind the head but do not strain the neck.
Grab both elbows with the forearms over the head and stretch upwards and back.
Try taking your forearm behind and across the middle of your back. Maybe grab your other arm. Do the best you can. Then allow the breath to lift the chest up. When the chest lifts notice the shoulder open, try to get the shoulder to rotate backwards slightly, all those parts are connected.
Constant repetition is important. Find a comfortable place in the stretch and let the breath do the work. You will also find it helps tremendously for sitting at a desk all day. Doing these intensely once a week will not be particularly helpful and may cause injury."