1. Get into a half-kneeling position.
  2. Squeeze the glute of the side that's on the floor. Think: belt buckle towards chin. This will posteriorly tilt the pelvis.
  3. Now scoot forward an inch or two, moving through the hip itself and not your lower back. That's a "real" hip flexor stretch.

The Wrong Way

When most people try to stretch their hip flexors, all they do is extend through their lower backs and defeat the whole point of the stretch. When you stretch in excessive anterior pelvic tilt, you're not stretching your hip flexors. You're stretching your lower back.

Also, the same people who do the stretch that way will always complain of feeling tight in their hip flexors. That's not tightness, that's you plowing through the anterior hip capsule, forcing the femur forward. That's protective tension you feel. And that crappy hip flexor stretch you're doing is only feeding the issue.

Besides, you'd think after several years of performing that stretch something would have changed by now, right? A hip flexor stretch doesn't entail crazy ranges of motion.

Related:  7 Ways to Fix Anterior Pelvic Tilt

Related:  3 Stretches That Make Things Worse