I started out with a pencil drawing and then inked and toned it in Manga Studio EX. If you haven't used that program, I highly recommend it. It is an amazing program for creating digital artwork, but especially comics.
Here's my rough pencil drawing that served as a basis for the final inks and tones. A few revisions were made during the process. I also had to stitch this piece together in Photoshop because my scanner wasn't quite big enough to get all of it.
Here's the final version of the image. Some compositional elements were improved as well as adding more depth with the rendering. I had a lot of fun working on this and got a little absorbed in the details.