Car Paint: Basics
Start with a Raytrace material, and use a "falloff" material for the diffuse spot.
Change the Falloff Type to "Fresnel". Change the top color to the color you want the paint to be, and the bottom color to solid Black.
Now back to the main material, and use falloff for the reflection as well. Again change the fallof type to fresnel. Leave the bottom color at white, and change the black material to a very dark grey (Value of about 15).
Back to the main material now, change the specular level to about 120, and the glossiness to about 60, and your ready to go!
This is my result from following this tutorial word for word, with a Max5 skylight and target light:
Now the paint is only going to look as good as what it is reflecting, so make your self a small scene, or use a good background image (HDRI, for very good results). This is using Max5's advanced rendering with a .hdr image as the skylight:
Mess around with the settings, and look at my other paint tutorials to get an idea of what all you can do with simple material properties. This tutorial can be used for other rendering systems as well, but some settings may be named slightly different.
Have fun with it!