Coloring question

I was told to ask this question about coloring here. I looked through the memories first but I didn't see anything that seemed like it was what I'm looking for.

Basically I went from a pencil artist to strictly photoshop. I want to start drawing again, but I want to be able to color the pictures I draw and scan in photoshop. An example of what I want to be able to do is
Photo Sharing and Video Hosting at Photobucket

Obviously I didn't do this picture. It was done by Teruchan on DeviantArt. (http://teruchan.deviantart.com)

I'm not really interested in the layering and such that's going on in the background. What I want to be able to do is take a picture that I have drawn and scanned, and color it like that on photoshop. I've tried to do it before by just using the lasso tool to select specific parts of the picture and filled it with whatever color I wanted. It came out looking horrible. If anyone can give me the steps or point me in the direction of a good tutorial, I'd appreciate it. I use Photoshop CS2.