Lower back... in my experience, my issues have always been SI (sacroilliac joint which is a float bone on either side of your side in your lower back). If it's only on one side of your back, try a series of stretches and this may give you more direction:
1) Stretch your hamstring
2) stretch your quad
3) Stretch your hip flexors
4) Try and stretch your glutes
Personally for me it's like it comes and goes. If I maintain my body fat ratio and keep fit it never bothers me. If I forget and loose myself for only one day. It kicks my ass. But when it's good for so long, you completely forget about your issue.
Like Praktik said, back problems are an obscenely personal issue, and it's different for everyone. No truer words have ever been spoken.
You just can't say. Get a Chiro! Stat! It's more lifestyle.