How can you beat back problems, particularly lumbago?

Be Proactive. There is no one thing you can do, good posture, body mechanics, exercise, stretching, weight control are all excellent starting points.
Not from just sittin. You need to be proactive beginning with lifestyle changes including: not smoking, weight control & regular exercise. A back support may help as well as over the counter medication as long as they are not contraindicated. You may heed to modify your activities ad well.