Best time morning and early evening. And I love to take pics with the cloudy sky. Dark clouds.
Don't ust a tripod unless it's night....
Some cars love to be photographed from below. Some not. But like TT said, experience is the best teacher.
And yes, don't use the flash. You'll murder the pic.
All in all, what the first two said 8)
Oh, and take as much detailed photos as you can
ops: I love them 8)