I know that the first response will be go see a doctor/PT/Chiropractor but lets move past that for now.
So my dad had back problems and I do as well. Couple reasons why are I have terrible posture and I sit in a chair all day at work then go home and sit in a chair all day on my PC. I'm in decent shape (5'10", 160 pounds) and I exercise 4 times a week. For back strengthening I do two exercises: Chin-ups and I'm not sure what the second is called but basically it's like a row. I stand and hold a bar around my waist then pull it up to shoulder level (the bar stays under the elbows).
For me my lower back is the main trouble spot. I've gone to PT who gave me some exercises to do (supermans, stretching, etc) but it was only a minor improvement so I stopped doing it. I've thought about yoga as well but never done it. At this point it's unlikely my posture will drastically improve as I've had bad posture all my life (hunch over). Other recommendations are getting a massage once a week which is not practical as it is far too expensive. Additionally, the PT I went to seemed like he knew some chiropractic stuff as he would realign my body and it was incredible how much it helped but sadly it only last about a day before I was back to having problems.
Anyway, I'm not sure what I'm really looking for but if anyone has some thoughts I'd be interested to hear.