Important things to remember before we start modeling...

When modeling a character that will later be used in animation, you will have to pay full attention to the topology of your model. Poorly designed models tend to deform very horribly during the animation process. As we will be starting with the face, you will have to pay attention to the most busy parts of the face: the mouth and the eyes. Topology around these areas has to be good.

Here is a few examples of bad and good face modeling.

This topologgy is excellent. THE edge flow around the areas i have mentioned: mouth and eyes is so perfect. You can almost see how the eyes will shut.

You will learn to appreciate the importance of good topology as you continue to work with animations and Shape Keys in Blender (or any other 3D modeling / animation software)

 Here are some more examples for you to compare between what is bad and what is good modeling...

This is also good!

 ...and so is this one.

You see, the importance of good edge flow around the eyes and the mouth is very important when you have to create things like facial expressions. A superbly designed face model will be able to tolerate any kind of deformation extremities your character's facial expressions may require.

And as you may well know expressions can tell a story without an Actor having to say a word.

These two images clearly illustrate my point.  

 If you still don't see my point do not worry, you will soon understand it when we get to animation.