I've done this a few times... You're really only checking cosmetic stuff, since mechanical isn't yet obvious (and is covered by the waranty).
Be systematic, and don't be in a rush to drive off. Work your way round the outside, check all the paint and in particular the wheels. Check the corners of the car, especially low down. Go into the boot, then sit in the back, then check thoroughly the trim in the front, especially the stuff you can't see (ie low down in the footwell).
I found: 2 scratches on the paint, 2 clips missing, 1 bit of trim not attached, one misplaced carpet.
Once I got it home, I found 2 deep scratches in the interior trim, so I'm not perfect at this!
Picked the car up @ 10. By the time I got out of the dealership it was 11'ish. Had a spin then had to go to work. I hoped I would get a good WOW factor in the car park, well put it this way,in the car park was my Civic a Megan coupe convertable and a brand new Focus ST. This is no word of a lie the Civic got more attention than the other two cars put together. The ST is a preformance car but with no looks...it a Ford Focus on steroids and the Megan is ....well its looks crap.
My Civic cost less than the Focus and Megan, has more gadgets and more people would rather have a Civc than the other two.
Now this leads to another problem. The car could become so popular that every Tom,Dick and Harry could end up with one and this would put it in the same class as a Focus...one on every street corner.