The best way to strengthen your rotator cuff muscles is to use the YTI's. Lie on a flat bench face down with two relatively low weights either side of the bench in each hand. Slowly raise the weights until your arms are in a Y position, hold for 3 seconds and lower. Repeat 10 times.
Repeat the same exercise again but this time bring your arms into a T position so your taking them out to either side. Repeat 10 times. The same is also done now bringing your arms back up so they are by your side. This is the I position.
To strengthen your elbow you need to conscentrate on your forearm, bicep and tricep muscles. For your forearms tie some rope to a weight with a bar at the other end, extend your hands fully infront of you keeping them straight. Twist the bar up until the weight has reached it and lower. Repeat until failure.
For your upper arm try starting with tricep dips and bicep curls.