first I start by simply sketching on an a3 size paper, if your wondering why its cut down in the middle, I still have a4 size printer.

then I scan through Adobe Photoshop and mask the image with a white fill and using the pen tool I ink over the image, I prefer to ink by computer and not by hand because it leaves a much neat and smooth texture.  

and then I just color and shade all over the image using the brush tool, pen tool, dodge tool and burn tool etc.