I use this stretch with my clients following a general warm-up or cardiovascular workout:

Here, I am doing a ‘dynamic’ meaning ‘moving’ stretch as I travel down the room, opening up, warming & increasing blood flow to my hips, knees, ankles & back. Keep the back as neutral as possible. Avoid rounding. It requires a bit of balance as you stand up from this position on one leg, step forward and lunge foward into the other with support from the hand on the floor. This is also fantastic used as a mid-run stretch.