When I used to work as a motorcycle courier in London, the sight of a diplo plate on, say, a 5 year old Mercedes, set alarm bells jangling like crazy.

As for the other "profiles" there is some truth to most of them, but they also tend to be dependent on location.
Delivery and service vehicles, the dreaded "White van man" Often, the job sucks, they get crap for not getting the schedule completed, and are often at risk of getting canned. The other thing is there are more of them than most of the others put together, given the tendency to just remember the bad, they sometimes get an undeserved rep.

While I am aware of the type of vehicle, I tend to be observing little clues like how they are positioned in the lane, signaling, ( or lack thereof ) that kind of stuff. Mostly this goes on at a subconcious level, and I will often find myself paying close attention to someones behaviour, before I've figured out what it was that set off the alarm.

One type that drives me crazy, are the parents dropping off their kid at school, and causing hazards in the attempt to minimize the danger to their little brat.

http://www.yehudamoon.com/index.php?date=2008-04-29