Here's a few I look out for.
Paint should be perfect. No details lost under heavy coats. Perfect shine. Not a good shine, a perfect shine everywhere. No ripples. If any bodywork modification has been done, it should be invisible. If a metallic color is used, it should be scale. A great paint job will stand out in any contest table.
Keep in mind a 2010 can be as shinny as a candy apple, old show cars as well. A 1965 Mustang? Not the same paint and not the same shine.