http://www.copperjoint.com/10-sure-tips-to-prevent-back-pain/

Lift carefully. The old saying “lift with your legs” is true in virtually all cases that require heavy lifting, so listen to the cliché and actually do it. This is because your back is spared the stress of straining to balance the weight. Bend your knees, tighten your abs, and hold the lifted object close to the body (but don’t turn into a slant board for it!). This is a relatively strain-neutral position that makes the more relevant muscles do all the work. Lift straight. Minimize the use of twisting movements when you’re lifting. These motions put strain on your trunk and thus your back. Even when not lifting, keep the twists and turns of your body to a minimum, as this can put undue strain on the spine.