"This tutorial will explain my workflow when making a normal map for a character. I'll be using 3DSMax though most of it will transfer to any program. As with everything I write, take it with a grain of salt, compare it to what you know, and figure out what you want to use from it for yourself.

First I'm going to explain what a normal map is and does, from an artists perspective. Imagine a styrofoam head that is faceted and chunky. This is like our low poly model. Then imagine coating it in clay and sculpting a much more detailed face on top of it. Then you slit this clay from the back, and pry it off. Lay it flat on the table, and you will see that it is thick in some places, and thin in others where the edges of the chunky head (the low poly model) came close to the surface. This layer of clay is what gives the definition to the sculpture, whereas it was featureless and flat before the clay was added. This is what a normal map does, though it is virtual and doesn't change the actual silhouette. It tells the engine how to display the light hitting the object. Current hardware can only handle a certain number of polygons still, but normal maps give us more detail without actually stressing the processors as much as trying to render the high poly models that the normal map comes from...."