"This isn't a battle anymore, its a motherfucking war!"

Okay :D

Shading is simple to do once you learn how to do it, like most things in art. You can probably shade using pencils, as can most people, but shading with a computer program is quite different.

What I do is, in a program like Gimp (For instance) is draw my object (duh) then get the airbrush tool. I select a darker colour than the original object, in this case dark red. Airbrush the side of the object farthest from the light source, taking care not to airbrush over the outline.

Then, I get the smudge tool. I smudge along the airbrush, pushing it away from the light source. Then you have the basic shading, but it looks messy. I make it look better by smudging the smudges into each other (Sorry if this is confusing, but it's hard to type up).

That's the best I can explain it, try it out and if you need help just pm me.