The Lips
1) Lower Lip. Place the fingers of one hand on the chin. Move the lower lip back and forth without moving the lower jaw (mandible) This will be harder than predicted but the hand holding the chin will give feedback about how much the jaw is moving. Try moving in all six directions (forward, backwards, up, down, right, and left.) Upper Lip. Repeat the movements as for the lower lip, this time holding the upper teeth to give feedback about the movement of the upper jaw. Then try holding teeth closed and moving both lips as much as possible. Using a mirror can enhance this.
2) With teeth open comfortably, open lips into a large "O" but not as wide as possible. Try shrinking and enlarging the diameter of the "O" until a point is found where the cheeks and lips tremble involuntarily. Let this happen a minute or two.
Rationale. The lips are not just padding for the opening of the jaw! They are separate organs of contact in themselves. Most of us, when asked to move our lips actually move our jaw instead, but that is missing quite a bit. Remember that lips reach and embrace, and jaws bite! Don't make the lips a softer version of the teeth. This is where kissing goes wrong for many. The lips of course are erogenous zones, with tremendous potential sensitivity. The lips are understood to be an indication of sexual feeling. Think of the famous scene in the movie Casablanca in which Lauren Bacall teases Humphrey Bogart about his inability to whistle. Woof whistles speak to this connection also. Whistling music has to be an excellent exercise for the lips, but the attempt will be frustrating until much agility and control is gained. The jaws of course do benefit from freeing also, but that is a separate freeing.
Source. Multiple