Their general demeanor: Apparel, posture, facial expressions
I'm with DW. People who cannot be bothered to speak properly and who use "like" in every sentence, etc. Who just repeat the same nonsense (only louder) when you genuinely cannot understand the garbage they are talking. Recently, my son took a trip around Holland, at every railway station, hotel, shop and public place, the people were able to talk to him in English. On coming home, he twice (on the same day) encountered workers on London Transport who did not understand him or his girlfriend. Welcome to multi-racial, multi-cultural England - It's a long road - perhaps we'll make it to the end.
Their attitude and manners.
There hair I guess.