Standing in a doorway. Take one arm out to the side at shoulder height. Pressing the forearm against the wall/frame (so it is in full contact shown in image), step forwards, opening up the chest and stretching across the front of the shoulder and chest.
Standing, facing a wall. Place hand flat against the wall at shoulder height. Gently push back through the shoulder blades (the shoulder blades will come forwards and you will feel a stretch between them).
Lying on a foam roller if you have one (or rolled up towel), knees bent up. Stretch your arms above your head and allow arms to drop down towards the floor, keeping your chest still. Try to relax into this position. Once the stretch eases, repeat in two further positions as images show, opening and stretching the chest.
Sitting straight and tall, slowly twist your upper body around to the side as far as you can go, take a deep breath there before returning to the centre and turning the other way. You are mobilising and stretching through the back.