If you are having shoulder pain, most likely the rotator cuff is involved. The rotator cuff is made up of four muscles: the supraspinatus, infraspinatus, teres minor, and subscapularis. They are very important in shoulder movement and stability. You can have a strain, sprain, partial tear, or full thickness tear of the muscles.
This video will show you some simple strengthening rotator cuff exercises lying down to get it strong again. You can use just a small amount of weights for these exercises. Start off lying down on your stomach where your arm can hang straight down. Put a small 1-2 pound weight in your hand. Keeping your arm straight, move your arm straight up to parallel to the ground or body. This is shoulder flexion. Then pull your arm back towards your side; this is shoulder extension. Now lift it out to the side keeping it level with your body. This is shoulder abduction.
Now you will roll onto your back. Keeping your arm straight again, and trying not to bend your elbow, punch your arm towards the ceiling. These are called serratus punches or scapular protraction. These muscles keep your shoulder blade, or scapula close to your ribcage and tracking properly. You can start out with 10-15 repetitions, and then work your way up.