First of all, I find a nice picture for reference.

I start out with a new psd of approximate dimensions as the reference. I make a nice gradient and some blurred and stretched noise for the background. Then, on a new layer, I do a rough paint to determine color and proportion.

I start adding detail to the front wheel and the translucent shirt. The technique I am using is to paint zoomed in close to the reference and on my painting. It is then much easier to capture the fine details of the reference photo.

I then tweak the silhouette and detail out the chrome, using the same "zoomed in" technique. I try to determine the colors I paint with by the reference with my eyes as much as possible. Occasionally, I will use the color picker tool on the reference to see the hard to determine colors.

More tweaking on the gas tank, forks, and front fender.

Trying to get the skin tones right, face proportions, hands, front reflector. I skip around to different places a bit so one section doesn't get more detail than others, and so I don't get bored doing only one thing to the end. It also helps to keep the whole piece unified.

Detailing the shirt

Here, I start the arduous task of painting the hair. Trying to see the hair in groups of strands works much better for me then trying to paint in single stands at a time. The smudge tool works wonders here.

For the boots, I created a new layer and painted the silhouette with a very dark grey. Then I took a grey, 1 pixel, feathered paint brush and quickly dashed in the strands of fur for highlights. I also pixeled in the details of the chain skirt. And it's finished! Check out a larger version.