The first secret is that I love forums. Who doesn't, right? But people in the real world never seem to understand - so I'm not telling anyone that I just spent several hours shooting my Forester for the subaruforester.org 2014 calendar contest.
But whatever - I figure you guys will understand.
The second secret? Use a circular polarizing filter when shooting cars. If any of you haven't used them yet, they're great. They allow you to control the amount of reflected light that your camera sees.
Here's the exact same picture with the same exposure and settings, just with different turns of the filter:
I combined both of these pictures with masks. I used the front end from the first picture and the rest of the car from the second. Adjust the levels, change the color balance, add some high-pass, and call it good. The result is that first picture I posted.