When drawing from life, speed is a required skill. It's easy to get bogged down with facial detail at the expense of the figure. Even in short poses, I like to create a reasonable likeness in the face, so I resort to caricature. To most people, caricature is a thing: a humorous and grossly distorted interpretation of the subject —like the ones you see everyday on the editorial pages. But it's also helpful to regard caricature as a quality of art (like drama and contrast) that can be used in varying degrees when trying to capture a likeness.
Lautrec and William Auerbach-Levy were masters at distilling a subject down to a few brushstrokes. Their art emphasizes key features not through distortion, but by eliminating anything unessential.
These three drawings were all done when the model was relatively new to me. They are attempts to focus on the face and learn what properties can be seized upon to get a reasonable likeness on paper in a minute or two. They are quick portraits using caricature in varying amounts of subtlety.