
Sit or stand upright.
Lift one arm up to the level of your shoulder.
Then, move that arm across your chest, so that the arm points to the opposite side.
Bring the other arm under the elbow of your crossed arm and use it to pull the crossed arm slightly towards you. This will give you a good stretch on the back of your crossed shoulder.
Hold this stretch for a count of 10 seconds.
Relax and repeat the stretch on the other side.