Power Cleans: The best thing for you to do is get a coach or someone to show you in person. This is a dangerous exercise if not performed correctly, and you should work on your form until you put on heavier weights.
1. Start with the bar on the ground.
2. Stand there like in deadlifts, but with your hands facing you and inside of your knees.
3. Make sure your back is straight. Drive up forcefully and fast.
4. Shrug your shoulders up hard with the bar and drop under it.
5. Swing your elbows under the bar as you bend your knees to catch it.
6. Catch it with your arms bent and straighten your legs to stand up up.
7. The bar should be in the position of a front squat.
8. Then slam it on the floor and do it again.
Box Squat: Just squat down on a box that's low enough for your thighs to be parallel to the ground. Then, as soon as you touch the box, explode up as fast as you can, but don't lock out your knees.
Speed Bench: Just press it up as fast as you can, but don't lock out your arms.
Rotator Cuffs:
http://familydoctor.org/265.xml