Always remember to exercise your better side first.
While lying on your back, bend both knees. Cross your ankle over/above your opposite knee. Reach behind the thigh (or use a belt around your thigh) of your leg that still has your foot on the floor.
Pull your thigh (or belt) straight towards your chest as far as you comfortably can. Then pull your thigh (or belt) towards your same-side shoulder as the thigh you're pulling. You will feel a strong stretch in your piriformis muscle, the muscle deep in the back of your pelvis. Hold for a 3 to 5 count. Relax for a 3 to 5 count. Repeat for 8 repetitions. Repeat on the opposite side.