Pictures should NEVER be taken indoors. Indoor areas do not allow the true colors to show. Florescent lighting is an absolute no-no. Outdoors on an overcast day, with minimum background distractions, is best, if the car is the focus of the pictures. You don't want a tree, power pole or fence post appear to be sticking through the car. No pets or other people in the pic, either; unless you want a "cutesy" look that only you are going to appreciate. Pictures on grass are bad, too. Cars belong on pavement or gravel.
I take pictures for an auto inspection company, so I try to find an empty (or nearly so) parking lot to do what I need to do. With that in mind, position the car INSIDE a lined parking spot, and do not straddle lines. THAT is very distracting, just like trees and poles. Or, position the car so that it looks like it's driving through the lot.
Turn the front tires away from the camera, if taking a shot with the wheel turned. Do NOT point the tread at the camera - it makes for a goofy-looking picture, plus it looks like half the wheel well is empty...another distraction.
Windows all UP is best! All down is OK, but UP looks best. If taking pics of a convertible, if the top is UP, the windows are UP. If the top is DOWN, the windows NEED to be DOWN.