Now that I've cleaned up my image, the next thing I do set up a new layer I can color on. But hold your horses, there still some set up you need to do before you can start throwing color around.
What I've done here is selected all the white space from around the character and deleted it so all thats left is the line art. This is basically a set up for a neat little trick later on. Remember to double click the "Background" layer so when you delete the selection you get transparent pixels instead of whatever the background color is. Computers are stupid, they don't know what you really want.