Glute Stretch
Many people neglect stretching their glutes. They focus on their hips and hamstrings, but glute tightness can also cause back pain.
To do the glute stretch, sit on the end of a bench (the ground will also work), bend one knee and bring it into your body.
This should be done for 2-3 reps of 30 seconds per side.
If you are suffering from poor flexibility, Joe DeFranco recommends stretching 2-3 times/day.