On a nice, flat desk. It's easier for me to draw on a flat desk than a tilted one. Supplies up top include a pair of compasses, scalpels, rulers of various lengths, french curves, various templates, lettering guides, triangle templates, a flexible ruler, a rack to hold my pens while working on a picture (instead of getting them scattered all over the desk) and a cup of various drawing pencils and pens. The little Nala cup was something I bought when I was working at a Motorola factory in my early 20's, and I got it because it was the perfect height to hold a selection of rubbing stumps for my pencil work.

The file rack has rough drafts, completed pictures, and important forms and other crap I'm working on. This is the desk I use most often when drawing.