This stretching exercise helps you to ease neck pains which is more effective if gentle pressure is applied using hand.
To perform Neck Rotation properly

1. You must be facing forward with your arms in front of you.
2. Clasp your hands together with elbows straight so as to stop shoulders from raising.
3. Turn you neck sidewards so that chin moves above your shoulder.
4. Hold in this position of 10-30 seconds.
5. A variation might be done by pressing back of your head gently with your hand.
6. Now do the other side

This video shows another variation of the neck rotation in details