Now that you have that first bone ready, aim constrain the rest of the bones in the chain to the next cluster respectively in the group, except for the last one joint because it has no cluster after it and it's not polite to point anyways.

Fig 9. Aiming the Joint

Finished that? Good. Now repeat the process for the other three joint chains. (Kinda reminds you when of when the teacher made you stay after class to write lines on the blackboard over and over again?) Don't worry, once you get a rhythm going you can do the whole thing in ten minutes, tops.

Once we’re finished all of that grunt work we should be looking at set of lip joints that stretch no matter how far you pull them and point towards each other in an orderly fashion. If you were me you'll also be looking at several empty beer cans and a week old burrito, but I digress.

Step4. Linking the Controls
The theory behind this facial deform technique is that the lip bones are driven by a hierarchy of control objects, each level of which has a specific function. Trust me, it's not as complicated as it sounds or I wouldn't have figured it out in the first place. First we'll make a set of controlling objects.

Create a control object made of NURBS curves, a locator, an empty group, or duct tape and baling wire if you so choose. I make my controllers with a triangle made of a single NURBS curve because it doesn't show up at render time and the duct tape/baling wire thing is difficult to get on the hard drive.

Duplicate it and arrange the controls in a nice symmetrical, organized fashion around the lips. I use eight controls for my standard setup: One for each of the corners, two for the middle of the lips (one top and one bottom), and four in between controls. I've tried to pare that number down in the past, but just haven't gotten the level of control needed. I also suggest you don't put any more controls than eight unless your character has an enormous mouth, or you’ll be spending the next month doing the animation setup.

Rename the controls to something convenient i.e. RightCornerControl, etc.

Centre the pivots for each one and Freeze the transforms so we get a nice clean bunch of zeros to work with in the channel box.

Now we get into the more complicated setup. Grab a controller and group it to itself.

Rename the group to whatever you called the controller with a "_SDK" suffix attached to the end. Renaming things in Maya is one of the few facets of life where it pays to be anal retentive. (Why it is that my Maya files are as neat as a pin but my office looks like a tropical earthquake hit it is beyond me.) This group will be the control that all your set Driven Keys will be put on when its time to set them up. That way you have a node for use with slider animation (for something like a 'sneer' or a 'smile') and underneath it you have a control that you can freely animate, but that follows along when you move the aforementioned sliders. You'll see what I'm talking about later, trust me.