A dirty car sticks out. When approached, if the inside of the car looks like a garbage dump it raises the officer's suspicion. I did notice that nowhere in the post did it say "Obey the traffic laws". I would think that would be important.
I would normally issue a ticket to somebody if they told me why i pulled them over. Example: "Do you know why I pulled you over?" "Because I was speeding." If they knew they were speeding (depending on the excess, location, and other factors) then they deserved the ticket because they knew they were in the wrong.