First you need to think of how you want to make them, Modeler, Texturer, Animator or Compiler you decide which one pull towards your natural ability or creativity, then you go on from there. Try find which one suits you best, then find a tutorial for it.

Hope I helped you.

Hardstyle.

Textures. what program do i need?

You can use photoshop for it but you need a .vtf plugin, you should be able to find it somewhere on this site

Hardstyle.

In this case, he is skinning for the Goldsource engine, and not the Source engine. All you need is Jed's Half Life Model Viewer, which is in the HL or CS1.6 tools section on this site, and a good image editing program.

Something

Wait you can't skins CS:CZ with photoshop and a .vtf plugin? thats strange, I thought you could.

Hardstyle.

Not exactly, the problem is that Condition Zero doesn't use VTF files, instead, model's textures are in it's MDL files.

Something

Ok, i think i get the basic idea on how to do this, but in order to get to the games models, i have to extract them from the .cfg file they are located in.

so what do i do after i edit the textures for the model?

Well, you need to extract them from the GCF file, then, to replace a texture from a model, it needs to have the same size, and be a 8 bit (indexed color) .bmp

Something