Answer:
I start with the head (a basic circle), add jaw, and then details. The neck would be two lines stemming from the base of the head, going down. Stop where you think it's proportional, and then add shoulders.
I've not yet learned how to draw a full body yet, but I tend to make the body parts first, such as arms and legs, then attach them to a body and the headshot.
Step-by-step explanation:
Hope this helped you out, artist to artist! :>