Character modelling is a funny old thing and I think it really boils down to what you're most comfortable with. I tend to go for a poly by poly route myself, but box modelling is certainly a good way of getting quick results.
I'm going to blow SimplyLightwave's trumpet a bit here and say that you've got a good couple of free tutorials here that lend themselves to basic character modelling:
Just click on the Video Training thingy then go to the Free training section.
The movies you'll want to look at are Peter Duncan's Creature Feature and Philip's basic head.
Alternatively, if you really want to get into head modelling, then you could go over to Newtek's own site and have a look at UserDelta's videos:
http://www.newtek.com/products/light...modeling/head/
Just go through these resources one at a time, and try and get a feel of what's going on. UserDelta tends to use the SmoothShift tool for virtually everything and spinquad. You'll learn a lot from them.