I dislike generalizing, but there can be a few giveaways. Some are very subtle where my brain is profiling and telling me someone isn't from around my area. Here are some more obvious things that are only sometimes true:

1) their base face is a straight face, just a more serious look in general 2) red face or nose, white skin that looks like it burns easily 3) raised moles on nose or face they felt no need to ever have removed 4) button down shirt with short sleeves rather than tshirt when it's a casual, bum around day. 5) real sandals over flip flops 6) May be thin, but doesn't necessarily do chest presses or have a stealthy appearance. May have good looks in face, but never done a bicep curl.