This video gives out some great tips on how to take photos at a car show. What to look for and what to avoid to get the best looking shots.
Things to look at when shooting automobiles on site:
Bright sunning days are almost always best.
Shoot small sections of the car at a time.
Find interesting parts on each car that draw interest.
Bring a fish-eye lens if you have one.
Try using bokeh effects to single out points of interest.
Let reflections be your friend and use them creatively.
Use HDR function during very contrasting light to not have blown out shots.