Gooberz's link is the exact modeling tutorial I used to learn character modeling. It's a great tutorial, and I still use the same technique for creating characters.
That being said, extruding from a solid box seems a more popular method (just judging from the number of tutorials I've seen in the past that cover the box extrusion method versus the "Joan or Arc" edge extrusion method). Here's an example:
http://www.brilliant-creations.com/yodatutp1.htm
There's another tutorial here that covers yet another method:
http://67.15.36.49/team/Tutorials/3d...isedhead01.asp
As stated before, I use the method Gooberz suggested. If you decide to go with that method, keep in mind that it's not the easiest when you start, but you'll get better with it after modeling a number of heads.
Also, whichever method you choose, you may want to pick up the Divide Loop plugin if you're using the Windows or Linux version of AC3D:
http://supercoldmilk.com/ac3dplug/divloop.html . It comes in very handy for head modeling.
Good luck