These type of movements help to stretch your facial muscles. There are several different ones you can try, however, one that I have found to be particularly effective is the jaw release. You perform it by inhaling deeply through your nose, then exhaling slowly with your lips tightly pressed together.
You can vary the exercise by moving your jaw in a chewing motion while you inhale and exhale. Be sure to pay special attention to your posture by sitting or standing upright. Repeating this activity 5 to 10 times a day will go a long way in helping you to reduce neck fat, so go ahead and give it a try!