you bake the diffuse. :D you set up a material so it has the reflections, shadows, chrome effects, refraction of the glass(plastic) and the bump. You might have to do it in layers and then put it together in Photoshop. I'm not sure how many maps you are planning to use, if it's just a diffuse, light up your head light as…
Rares: here's some tips from me: First one I ever did was a Porsche 959 taillight, couldn't find any good picture for a texture back then. Here's a crop from the sheet: You need to FULLY understand how the light is built, because you should paint it up in layers. I started this one by first painting a flat representaion of…