honestly, it's usually just a matter of taking a base color and then taking one high variation and one low variation of it. from there, you just imagine the character is facing the sun and you adjust for shadows and highlights! like i said, you get better with it as time goes on.
i bet he's probably a lot better than me, haha. i used to look up tutorials and things a long time ago but i've forgotten most of them. i can't make anything too fancy.