FYI, I've posted a quick face test video to show the edge extrusion technique in AC3D.
http://media.putfile.com/Face-example
The video is about 10mb, so be patient.
Keep in mind that the model in the video was thrown together rather quickly, and an Orth background image was not used as a guide (which I'd normally recommend, and it's almost required for your first head model). As a result, I don't do a good job of following natural facial contours. Check out the earlier link I posted showing the Joan of Arc head model for a more natural contour example.
The video starts out with a simple rectangle creation. Edge extrusion (Ctrl+E) is used to create most of the model. Hitting Ctrl+E extende the selected edges, which are in turn selected so you can quickly move/size/rotate them.
I don't remember how often I use it, but at around 8 minutes into the video you'll see the use of the Create Quad (Ctrl+R) function, which creates a rectangle from two edges connected by a vertex.
Also, I use Create Ordered Surface (Ctrl+S) to create a surface from 3+ vertices.
I dont use it here, but the Divide Loop function is also invaluable for adding additional detail.
This is not a terrible guide for creating faces until the 9.5 minute mark, where I make a mess of the forehead and waste my time fussing with it rather than rethinking it. However, this should give you the idea. Also, keep in mind that using a background image makes this a *much* simpler process.
Dennis