I've been studying up on facial modeling for the past few months, learning about different methods of modeling (starting from polygon primitives, polygon profiles, nurbs spheres, or subdivision surfaces) and facial modeling theory (orthographic drawings, edge loops, polygon counts). I started in on a few tutorials, but nothing was really working out - the heads looked funny or became too complicated too quickly.
Then my professor clued me in to a DVD that character artist Mayan Escalante put together for the Gnomon Workshop. I watched him model a low-polygon game character head, narrating the process in real time, and everything clicked. Escalante models by creating a few key edge loops - the closed, overlapping contours that define a wireframe model of the human face - around the features of the face, and then connecting them to create the full volume of the head.
For whatever reason, this method made the most sense to me. So I drew up some orthos based on one of my spacemen -
And set to work. Here are the results:
This wireframe view allows you to see the edge loops, which flow from concentric circles around the eyes and mouth:
I worked on this over the course of about four 2.5-hour sessions, so I'm guessing the final model represents between 8-11 hours of work. Hopefully the next head will go faster and have even nicer topology.