Chewing

Let me try to present a simple chewing shot.
It was done in about 2 hours, and I have to call it a day, so there you go.
The point is to create a short shot with cycled chewing.
Let's get the character, position it close to the camera, parent his Head and Arms to the Root, create Quick Select Sets, select the controls and make our first key on frame 1.
Now let's act. How about making life reference video shot of ourselves chewing? Then use the method described in "Using Video Referencing". I'll skip this step for lack of time.
So after setting the keys, playing with timing and inserting holds my acting looks like this.

Red rectangles are the holds ( I used Middle Mouse Button (MMB) "drag and drop" function)
Note gray selected controls in the Outliner. These are my Quick Select Sets.
And it looks like this:

Here are two shots with the Root area visible. Never forget about the root compensaton when you bend upper body. A see-saw effect. Upper body bends forward? Move the root backward. 

Take a look:

Sideways

Upfront

I wasn't very satisfied with it and kept on playing with holds until I got something like below.

(Note that I decided to get rid of one of the holds, in yellow oval.)

Time to create moving holds. Again, I used MMB drag and drop.
This is enough for the body language, next step is lip sync. I'd leave the eyes and brows as is.
























Now I'd go right in between the holds and insert the jaw movements. It will give me sharp chewing movement with holds. May be I will have to move the holds a little. Facial animation doesn't necessarily coincide with the rest of the body. I started by aligning all keys for simplicity of playing with timing. Now, timing is done and I can play with mouth shapes and chewing timing. I begin with jaw movements, then, giving the character more or less civilized attitude, I'll keep his mouth closed.

Red rectangles 1, 2 and 3 are the "down" movements of the jaw. Green rectangles 4, 5 and 6 are the holds.
The result is Here
I think I'm done for now. Note I haven't done anything with the eyes: blinks, change of eyelids shapes, eye darts would greatly improve performance.
But the most important element of the approach is to start with the body motion, then add the mouth movements. In some cases, you start with the lip sync, then add body animation. But something tells me it's better to be done the other way around.