Real Time Character Modeling Tutorial
Face topology is very important, depending on what you wish to achieve with your model that is. A good rule, as with the body, is to stick strictly to the muscle structure when placing your polygons and edges. Paying attention to how the face creases, and constructing it according will give you a natural looking face as well as making the creation of blend shapes and animation easier and more fluid.
Face Muscles Face Wrinkles
Once again, import some scanned in imagery to use as a guide. Scale the image plane to fit the rough head you have created:
Subdivide the faces at the front and start to move the vertices until you get the general shape. You should also do this from the front view, using another image as a guide.
Splitting the polygons, keep adding more detail until you are happy with the way the face looks, remembering to keep the edges running along muscle lines and also bearing in mind how the face will need to deform i.e. will it need eyes, eyelids, an inner mouth?