A good low-poly head:
http://67.15.36.49/team/Tutorials/future_worker/futureworker_01.asp
But since you have more polies you'll have better topology, especially since yours is meant to animate.
But even better are books. I suggest, from my collection:
Stop Staring (book)
Building a Digital Human (book)
Advanced Maya Character Modelling
Gnomon Game Character Modelling (and Head Modelling)
And choose a next-gen game (such as HL2), figure out how to import the characters into your program, and study them. This will first teach you about the game art pipeline, which is a big deal, and second, give you great reference.
Be careful what books you choose, and make sure the people who recommend them know what they're doing. Paul Steed's book looks like it blows... a similar book was Maya Character Animation, which had extremely strange and inefficient methods, and was recommended to me by a modelling professor... needless to say, she was woefully unqualified, and I wasted $40.
Your goal is a mix of both. Again, look at models. For an idea, this is a quick character I did a little while ago, could use some more geometry in some areas (with weapon about 3100 polies), but this sort of distribution and flow is what you're going for (shoulders could be better).