Once the track is read, you're ready to begin animating the dialogue. Dialogue is slightly different from lip sync because lip sync simply involves the lips. Dialogue, however, involves the whole character. When animating characters, be sure to get the character's entire body into the acting.
With the body so important to dialogue, one of the questions that you might have is whether to animate the mouth or the body first. Some animators simply do the mouth first, just to get the tedious task out of the way. It also is easier to get the mouth animated first on a still head rather than one that is moving. Other animators like to concentrate on the body first and then get the mouth. Both approaches work equally as well, and because you can always go back and tweak the body and the lips independently, the line between the two methods is pretty much a gray area.
Animating the Mouth
If the track was read properly, the phonemes and their location are pretty much known. In the track we just read, for example, we might know that there is a gasp at Frame 22 and the word Oh at Frame 42. One important trick that will work to your benefit is to always try to open the mouth quickly and close it slowly.
Vowels are those points in speech where the mouth opens. When animating a vowel, you need two positions. The first position is the accent pose, when the vowel is first uttered. The second position is the cushion pose, which happens toward the middle to the end of the vowel sound. The accent usually has the mouth open wider than the cushion. One good way to do this is to animate the jaw so that it closes slightly as the vowel progresses. For fast vowels of only two frames, this may not be much of an issue, but this rule applies to anything above four frames.
Consonants are those points where the mouth closes. With the possible exception of a long M, F, or V sound, most consonants are only a few frames in length; some can be less than one frame long. With this in mind, make sure that you leave each position on the screen long enough for the audience to read them. Consonants must be on the screen for at least two frames to be read. If the consonant is too short, steal time from a vowel or combine two consonants into one.
Eyes and Dialogue
Once the basic lip sync is accomplished, the eyes are next on the list. When animating eyes with dialogue, be sure you understand where the character needs to be looking. Ask yourself the question, "Who is the character talking to?" Try to keep the eyes focused on the subject at hand.
Head Motion and Dialogue
The head moves quite a bit when people talk. The head will bob, nod, and shake to emphasize certain words in a line of dialogue. When speaking loud sounds, the head usually raises to help open the throat. This is helpful when animating the loud sounds or accents in speech.
When animating an accent where the head raises up, it is always a good idea to anticipate the motion by lowering the head three or four frames before the accent and then popping up the head on the accented syllable. This is also known as a head bob and is usually accompanied by a blink. To get more action into the head bob, you can also get the body into the action. As the head moves down in anticipation of the accent, raise the shoulders a bit. As the head pops up, lower the shoulders.
Body Language and Dialogue
When talking, many people use their hands to clarify and emphasize the major points of their speech. Getting this part of the animation correct is a lesson in acting. If you want to see how not to animate, watch some really nervous or first-time actors. They usually are very self-conscious, stuff their hands in their pockets, wring them nervously, or hang their hands loose at their sides.
In real life, body language precedes the dialogue by anywhere from a few frames to as many as 20. Generally, a slow, dimwitted character has more time between his gestures and his dialogue than a sharp, quick character. Speedy Gonzales has considerably less of a lead time on his gestures than Forrest Gump. Someone giving a long, boring speech will be much slower than a fire-and-brimstone evangelist.
You should also make an effort to ensure that your gestures fit the dialogue smoothly. The first gesture every animator learns is the ubiquitous finger point for emphasis, followed soon after by the fist pounding into the palm. These gestures certainly have their place, but within a much larger palette. Simply watching people in their natural habitat is always your best reference.