Each car should have had 3-5minutes spent on it - any more and there would have been no time to judge every car.
That being said, I do the same thing when I judge every car: Introduce myself, ask the owner to open everything up that they want too (while I do a quick walk around looking for dings, scratches etc). Usually start at the engine bay - look for mods, are they installed well, do they look stock? Is there wiring all over the place? It is clean?
Then move to the interior - I crouch down at the drivers door to look for dirt, look at the headliner, the stereo install, seat wear and tear, and look for mods - again, I should be able to see them, but they should be neat and tidy and look like it could have come from the factory.
Moving to the rear, there's usually not much to see, but if you are on air, it should be done correctly, correct tanks, valve, solenoids, all wired nicely as well. Having a hacked together air system will lose you points.
Lastly I do the outside, look where body panels line up, look for orange peel on areas that were repainted etc.
Finally - can I tell what the owner was going for in their concept. Some people go for OEM Euro goodness, while others go for high end fit and finish and big audio. Both concepts can score equally well - if things are done right.
As said above - having $3000 wheels and Airride isn't going to win if your interior is dirty, you've got nothing special in the bay, and your body panels don't line up. In my mind, every car starts with half of the points available in each catagory, and works up, and sometimes down, from there.
It helps that I usually judge 100 or so cars a year as various shows, and can spot most mods far before thier owners mention them (even things like reprays which are sometimes tricky) but even a novice judge can get things 'right' when they use the same metrics for every car they look at.