Hack
I have no training, so I just hack away at it. My process usually starts with a light pencil sketch, a wireframe of sorts. Then I'll sketch in overall shape and details over that. Next I begin to refine the details and use erasers to remove some of the wireframing and early sketchwork. If the drawing has survived this far, tracing paper comes out. I trace over the pencil sktech in pencil again, preserving only the lines that are "final". Finally a pen comes into play. I trace over the pencil outline on tracing paper in ink to arive upon a nice "clean" version of the drawing. If the confluence of inspiration and ability continues, I may take the ink and scan it, which I then color in Photoshop (using an entirely different practice of hacks).

What follows is a look at how I take a concept from pencil sketch to ink and finally color. (You may notice lego-men-like sketches in the upper left; these were Carole's conceptual layout of her characters)