For me the first thing is cleanliness. If the car isn't clean, even if is the best car in the class, I may not vote for it. I have voted for cars in some participant vote shows solely on the number of bugs in the radiator. If you don't take the time to clean out the radiator, the car isn't clean.
Tied for first is presentation. If I see a car in a participant vote daily driver class that obviously isn't daily driven, I won't vote for it either. It has to be obvious though, detailed undercarriage, no rock chips. It isn't hard to figure out if the car is daily driven or not.
My second criteria is a combo of cleanliness and presentation. If there are multiple cars in the class, and one does not have the hood up, I won't vote for it. Even if it has the most beautiful paint job in the world. If there are two cars in the class and one has the hood and trunk open and a so-so engine compartment and the other doesn't, I'll vote for the car with the hood up becuase I assume that if the hood is down, it is filthy, or the owner would have it up.
Worksmanship is third. It must be tasteful and well done. If it is gaudy, I probably won't like it.
Fourth is a competition thing. If a car is obviously the best car in the class, and the next two cars are no where near the first place car, but are somewhat even, I will sometimes vote for the 2nd place car to even out the spread a little. If everyone voted for the best car, how would you figure out 2nd and 3rd besides the owners vote?
Just my opinions.