We start with a totally round head.
Then, draw on the eye line to show the position of the head and where the character is looking. You can now draw a very simple version of the torso, almost like a pillow. The small fold on the stomach helps to show the body position.
Now add the arms and legs, thinking about how they all articulate at the joints: the shoulders, elbows, wrists, hips, knees, and ankles.
By adding some neat details, we get this little guy washing his hair. Even in this really simplified drawing, the little line by the armpit shows where the arm muscles and the pectoral muscles connect—and it provides a real sense of movement.