the basic rules always make for keepers - having the wheels turned away from the camera so more of the wheel is visible, shooting at the right time of day, good exposure, shallow depth of field (sometimes) and lack of messy reflections on the car (maybe with a polariser, though some such as PhotosGuy preffer not to). But if you really wanna take it to another level, imo, try considering colours. photographing your yellow car against a blue backdrop would make it stand out alot more, as blue and yellow are opposite colours on the colourwheel and contrast more (hum, my designer side shows).
http://www.colormatters.com/colortheory.html
this link explains colour theory if you are interested lol.