Here's a tutorial that shows how I work.
1. I start out with a black and white grayscale image, I try to get an interesting pose, and then work on the values. Its pretty loose at this point, I try to not get too detailed at this stage and focus on making it look cool and alive.
2. Then color with a variety of gradient maps in photoshop. You can see the gradients are all very different, they don't all go to black, and they are also clamped at different points, which will make things look softer, or crisper depending on the type of surface you are trying to achieve.
3. I then paint on top of this colored image and add detail and clean things up. At this point the picture is basically done, and its a matter of cleaning it up and adding extra highlights and polishing it up.