All the people passing by get in the way all the time so make sure you get a photographer's pass and enter before the show officially starts for the day. If you are a regular visitor and want some nice shots here's my advice:
- Do close-ups of recognizable parts and insignia but never only insignia and never just parts. Try to make the brand and car itself look complete and recognizable without showing the whole thing.
- When you shoot under the hood try and get some branding insignia as well. It will draw the attention of all the people who know nothing about engines as well and will make the photo more interesting. If all is custom then get some curves that look interesting and could bring up some associations like a female body, a revolver's drum (like in the bottom left photo) or anything that people could unwillingly tie to something they know. The photo of the engine will not roar or smell like oil but if taken in an interesting way it will go deeper than the scent or noise of a revving engine.
- Watch for the reflections off the car's paint or chrome parts. You really don't want other cars there to be recognized or people's distorted reflections in your shot. It looks worse than having them in the background.
- I like using shallow depth of field (wide open aperture with values between f2 and f4) when I shoot at car shows because I really do not wish to have all the folks and other cars in the background having any clear lines. I shoot car by car and need to keep things simple so I blur what I do not want to emphasize on using wide aperture value.
- Do not use a (friggin') flash! Most of the times it will give you reflections that you really do not want in the photo.
- Watch for your own reflection. You need to be like a vampire - no own reflection in the shots.
More samples here.
All the best,