For 12 years I've done these stretches every morning before I get out of bed, I got them from Physicians Neck and Back Clinic in Roseville MN (click for full size):
I don't bother with the wall lean stretch in morning (see below) and I combine the standing thigh stretch with a freestanding balance exercise of pivoting forward to stretch hamstring.
In the evening I do 30-40 back extensions on a 45 degree roman chair. The first 10 are unweighted, the next set I use two 15 lb dumbbell, then a set with two 25, then a 25 and 35 (I need more dumbbells). Between sets I do lateral plank with hip dips for 20 sec each side (this was impossible when I started but now the only problem is some right wrist arthritis but if that's bothering me I do a straight wrist fist plant).
The editorial comments
My experience as a physician who treats people with back pain and as someone who has had some success with the problem is that nobody wants to hear that fitness is (almost!) the only fix. I get it, twenty years ago I also thought of this is an unfixable problem too, but at least since 2009 this has been common knowledge. The surprising bit is how much exercise it takes.
My back isn't bulletproof. I've had several episodes of back pain over the past 12 years. The most worrisome was seven months ago and was probably an L5/S1 disc prolapse. That took 6 weeks to mostly heal with diligent exercise and 10 weeks before I could set new CrossFit personal weight lifting records. I think I have some residual left foot extensor weakness (had to switch from low support CrossFit shoes to real running shoes for runs). On the other hand I play ice hockey, do CrossFit Olympic lifts, and basically expect a lot out of a crummy old back.