Draw the Sword
This is a good exercise for the rotator cuff, one of the shoulder's potential trouble spots.
Start in your "relaxed stance" as mentioned earlier. Place a light dumbbell in one hand and place that hand, palm down, on the opposite thigh (for example, put the thumb of your right hand on your left thigh). Keep your arm straight throughout this exercise.
Draw your arm across your body (out and up to above your opposite shoulder). Once your hand has reached a level above your shoulder, return to your starting position.
Perform this exercise slowly. Complete 12 repetitions, and make sure you switch arms.