It's just a matter of looking at reference material, and duplicating it. Buy a mirror, and google human anatomy, and don't worry if your first model comes out like crap.. it may take you 3 or 4 attempts to get a figure you are really happy with. And with each model, you won't duplicate previous mistakes. Like anything else, it just takes time, and practice.

Way too many people take way too many things way too seriously.