Remind them to draw ears as seen from the front. Eyebrows tell a lot about a person's mood. A gentle arch over the eyes should do for a relaxed face. They stretch over the whole eye or more. They are wider in the middle of the face and get thinner.
Most people draw the neck too thin.
Start at the ears and gently curve in then out again. If you have room on your paper, you can draw shoulders or part of the shoulders. You could stop now if your subject has no hair. But if he or she does, remember where the hairline is. Have everyone find the hairlines on their foreheads and then pat the top of their heads.