For starters, let me introduction myself. My name is Tommi Kaikkonen and I am from Finland. I was born in 1990 and I've been doing 3d actively for the past 2-3 years. I'm self-taught, so I've learned everything I know by the means of Internet tutorials or by trial and error.
1. Gathering reference
2. Basic modelling info
3. Creating spline guides
4. Modelling the head
Part 1: Gathering reference
This part is very important, because reference is the key, even if you would use it loosely.
Google's image search is always your friend, I get over 50% of my references there.
I can also recommend a few places like movieweb.com and 3dref.com, but there are many of them and this tutorial isn't about them.
Once you've gathered your references (and copied them onto your computer) you can scroll trough them and look at them. Then you can open photos that are from profile-view and front, and crop them for later use with a 3d program.
Part 2: Basic modelling info
Generating an efficient modelling technique is most established by modelling. This tutorial is done with polygons which are supported by almost every 3d program nowadays. My workflow is pretty much expanding the geometry from one polygon or a tubetop. Then I add detail by selecting an edge ring, and connecting it (if your 3d program doesn't have this option, you can do it by hand with the split tool), and then tweaking the new edges.
I don't really recommend my technique for beginners in 3d because the technique needs a good understanding of the mesh's shape before modelling it. And if you dont have that, you will have quite a dense mesh in the end to tweak. So I recommend first getting some reference and reading anatomy books. I also recommend to make a lighter mesh than I did :)
Also the topology of the head (flow of edges) is quite important, especially if animating.