Many people develop tension in the muscles along the back of the neck (posterior aspect) and across the top of the shoulders.  This stretch will help loosen up the muscles along the back of the neck up to the base of the skull.

To perform the cervical flexion stretch:

1. Start by actively bending your head forward to tuck your chin to your chest.
2. Once your chin has travelled as far toward the chest as possible, gently apply 1lb. of additional pressure to the back of your head using your hands.  This will provide just enough stretch to the posterior neck muscles.
3. Hold this position for 1.5 - 2 seconds and return to the neutral position.

Repeat the above steps a total of 10 times.

Make sure you aren't curling your upper body forward to compensate.  I usually recommend you sit in a high-backed chair and keep your shoulders in contact with the chair during the entire duration of the stretch.