Zypher - Spiffy

Original can be found HERE
So I was following tutorial on how to shade after doing your flats(which I did in Illustrator). Didn't get past the 2nd step, I ended up trying something my own way. I must say I did pretty well, for a background, and Stroking text. As for the shading on Zypher, I'm sure you, the viewer, will agree that I lack shading abilities.
I know what a light-source is, but I just can't see it.
I need a tutorial for that if anything. I think that's what most people struggle with, light-source. Rawr, I need help with it, anyways, comments appreciate my faithful viewers

Zypher © Me
Zypher drawn by: Tentionmaru