well if its judged try to bring some extras...
Clean the car, and Armor all the tires, even the tread!
Clean thoroughly under the hood, (hoses and firewall tend to look nice if sprayed with armorall but be careful not to get it on the car or its a PAIN to clean off at a show)
Clean interior (dont hide anything under theseats) and Vacuum
Clean trunk, be sure you have a Spare, Jack, Small Tool kit, Quart of Oil (empty is fine), Small one Gallon Gas Can (empty is fine), and a bottle of anti freeze (empty is fine), Fire Extinguisher, First Aid Kit, All points for a true judged show.
Clean inner wheel well's and also the frame under the fenders/door/1/4 panels (depends on the judge but they sometimes check for dirt)
Have some Memorabilia, I bring the owners manuals (all the crap in the glove box, and display it on the pass seat in a neat fashion), maybe a GN model (unbuilt and in the plastic or not), maybe a magazine or 2 with a GN on the cover.
Also key if you have a window sticker, bring either it or a repro and keep it out of the sun but visible (like in the trunk) so when being judged they see you took enough care to show it properly.
I dont tend to bring trophies to shows, but alot of people do. its more of a personal preference. (unless its a big indoor event where my display counts for something)
here is a pic of my car the last show it was at.