I agree with Hopkirk...bad posture is often a culprit.
My back pain improved enormously when I stopped leaning forward to peer at my desktop and sat back against my back support instead.
My friend is currently suffering with a really bad back and she's bought a girdle thing with magnets in from a cheapy shop - she says it is a big help.
Depends largely on whats causing the back pain. A muscle spasm is one thing, a torn disk pressing on a nerve something else. Them of course you have major structural defects of the spine. Find out whats wrong.