The hamstrings are gererally a tight muscle group. Although it is important to keep them strong they need to remain flexible as well. Tight hamstrings may contribute to low back pain and poor posture if not kept relatively loose.
To begin the stretch sit on the floor or on a bench and extend the left leg forward. The toes of the left foot should be facing up and not turned out. The knee should be fully extended. The first photo at the left shows this beginning postion.
The next step is to make sure that your torso is as straight as possible. Any rounding on the back will compromise the effectiveness of the stretch and could also strain the low back. After your back is straight hinge forward at the hips and bring your torso toward your knees. If you keep your back straight you will feel a good stretch through the hamstrings and possibly even into the calf.
The second photo at the left shows the stretch postion. Reaching for your toe may enhance the stretch as long as the back doesn't round. Hold the stretch position for approximately 30 seconds and then repeat on the right side.
The third photo at the left shows Bud in the start positiion. He maintains good posture and his toe is relatively straight. The fourth photo shows Bud in full stretch position. He is able to hinge forward slightly and it is enough to allow for a good stretch. Bud's hamstrings are tight but notice how he doesn't compromise his erect posture just to touch his toe. This is an effective hamstring stretch.