I decided to make this tutorial, as it's probably an issue that's overlooked by a lot of people. If you've picked all the colors you wanted to, and bothered with things like skin tone, and the picture still doesn't quite look the way you want it to, it's probably because of bad lighting.
EDIT:...Oh wow. That's what happens when you get a DD. Thanks though.
And for those who are wondering, yes, that's Hohenheim. Not that it even matters. I'm surprised he's that recognizable, even though I drew him without the glasses. I excluded the glasses because I just needed a simple example.