Roger Vernam wrote and illustrated a book called Drawing People for Fun and published it in 1943. He really does make the process engaging and fun through the use of simple techniques to develop your skill.
The illustrations shown give several of his building blocks to drawing the figure.
Plate III - Learn to think of the torso in terms of two separate block forms that move independently of one another.
Plate IV - Action of the torso: look immediately for the curve of the spinal column, the slant of the shoulders and hips, the rotation of the body due to the twisting of the vertebrae.
Plate XVIII - Life class studies: notice the frequent recourse to the block form convention.
Another blog with more illustrations is at The Pictorial Arts.
You can buy a copy of Drawing people for fun at Amazon.com