* Exercise. This will keep the back and abdominal muscles strong and supple. Swimming is good, but any other trunk exercises will also help
* Posture. Don't stand or walk in a bent-forward position, but keep the shoulders and head slightly back
* Sitting. At a desk, your feet should be able to rest flat on the floor with your knees bent at 90 degrees, perhaps even with your knees slightly higher than your haunches. Sit up straight, and use a chair that swivels
* Sleep on a firm mattress
* Lifting and shovelling. Bend at the knees, using them as a lever, while keeping your back straight. In particular, avoid twisting while lifting
* Excess weight puts extra stress on the back, so lose it.