The answer they gave me was accurate, if not complete. "It's hard to do."
People are just about the most difficult thing to draw well––especially portraits. Artists need to train many years to master this skill. And, it matters because, as in literature, most themes and topics involve people.
To draw the figure well, you must learn about the human body's anatomical structure, how it works, moves, how it relates to gravity, how the parts relate to each other, as well as a great many other concepts. The following video series is the best I know at teaching these crucial lessons. They have been produced, free of charge, by Stanley Prokopenko, teacher at the famous Watts Atelier of the Arts in Encinitas, California.
These videos contain partial nudity.
They also contain the best education and production value you could hope for. Remember, if you want to draw people well, wearing clothes, then you have to know what they look like underneath their clothes.
We're all extremely lucky Stan decided to make these videos, and I hope that all who view these videos will react in the same respectful, tasteful, and professional manner that he does. This video series is incomplete, it's a project he started about a year ago. I will add updates as he does. If you follow along with these videos, draw what he draws, and practice the exercises he gives, you will eventually be able to draw figures at a professional level.
SIMPLIFYING THE FIGURE:
A large part of art making is learning to simplify what you see. The figure is a very complex configuration of shapes, and you have to learn to see its over-all gesture/sweep/thrust. The following videos explain how draw gesture, and common mistakes:
THE ROBO BEAN:
This video by Scott Waddell shows how to use a pencil to measure a figure's proportions: