Best thing that has helped me was to stretch my hamstrings. That large muscle can pull you out of shape. For example, you have some sciatic pain and you start favoring a position that alleviates it. This is where the hammy comes in. Without stretching them, they will stiffen and start pulling the lower back into a position that isn't good.
Try this...
Get on the floor, and put one leg up on a wall and the other straight out. Slowly inch your butt closer to the wall while getting your upright leg as straight as possible.
Trust me, it works. Best thing I ever did!