HOW: Use a towel wrapped around the desired area of your neck to be stretched. The edge of the towel provides great friction for this mobilization. First stabilize one end of the towel, then pull up and over with the opposite arm of the desired side to mobilize.
For example, if the goal is to mobilize the left side - grab the towel on the left side with your right hand, pull angled upwards towards your right side leading with your eyes.
FEEL: In the example stated above, you will feel a stretch on the left side, particularly underneath the towel.
COMPENSATION: Avoid moving your head forward, backwards, or side to side - this exercise is designed to be purely for rotation. Make sure the arm that is stabilizing does not move and stays in place.