Dont smoke. Smoking increeases dddz.
Conditioning/Ergonom. Conditioning and proper body mechanics are some the best ways to prevent mechanical low back pain (ie sprain/strain). Other causes of back pain such as kidney infection or metastatic cancer of course will not be affected but are relatively rare in comparison to sprain/strain injuries. The more physically fit and the more you prepare for a certain task/activity, the better off you will be.