First car show -- advice??

Everyone is giving sound advice, go in there with the plan of having fun and being proud of your car. Lots of people will be wanting to talk to you about your car, be friendly and not arrogant or rude, regardless of the comments you hear. A cooler with drinks/snacks will definitely be a good idea, a chair or chairs if you wont be alone, and bring some cleaners in case you find a spot on your car that you overlooked when cleaning, and a Swiffer duster for obvious reasons.
Like @ProjectBazza said, if the show doesnt have assigned stalls, be early so you can grab a good spot.
And if you dont expect to win best of show, you wont be disappointed :)