Medium Difficulty (basic prior knowledge of 3D modeling assumed)
You will need your own 3D model of a person.
If you want to put textures on to your polygonal 3D model, then you need to create a UV texture map to make sure the textures line up correctly, otherwise they will appear stretched and blurred. It is fundamentally important because you will use the same map for colour mapping, bump mapping, specular mapping, etc. and you can't change your UV map after the textures have been made because the textures rely on the position of the UV map.
Texturing a 3D object is like wrapping a present or designing clothes for a body. You need to be able to wrap one or more 2D surfaces around a 3D object without any overlaps and also with the minimum number of seams that covers the whole 3D surface. This is easy to do with a 3D box, but something as complicated as human anatomy is a lot more difficult, but is based on the same principles.
Why are they called UV coordinates? Our usual 3D coordinate system parameters are called x, y and z. The three letters before these in the alphabet are u, v and w. Textures are 2D objects so we just drop the w part and simply call them UV coordinates.
There are many ways to setup a UV map, but here is a method that has worked for me.
Step 1: Apply the temporary grid texture to the model
Given a 3D model of a human, we are now required to set it up for texturing by defining its UV coordinates. The best way to see if your UV map is lined up correctly on the 3D model is to use a temporary texture of alternately coloured squares like a checker board. This is so that we can instantly see on the 3D model where the problems appear because we know it should look like a square. I have made my own grid texture that has more colours than just black and white plus it has directional arrows to help me visualise what's going on.
I am using Maya 7 in this tutorial for demonstration purposes but the process is still the same for all 3D software.
We initially use a Planar Projection map just because it arranges the UV coordinates into a recognisable form, plus it's quick and easy. We could use a cylindrical projection but we won't be using the automated projection in the end for our UV map anyway so it doesn't really matter - we will be unfolding and working on each section independently.
Make sure you are using the Modeling menu set. Select your 3D model then go to Polygon UVs > Planar Mapping
Change to the Rendering menu set. Select your 3D model then go to Lighting/Shading > Assign New Material > Blinn. It doesn't really matter which material you pick, so long as you can use it to apply a colour texture map to your 3D model. I like to use Blinn by default for most materials because it has a Specular option for shiny effects where required.