Clothes, Africans.

A friend visited some people in Iowa City, and she was saying her friend's younger brother is finally supporting himself as an actor in New York and doesn't need to wait tables and shit like that. His big adjustment to New York, though, was to figure out which brands of consumeable goods he needed to wear around and to auditions, since people would look at what his shoes were and what his jeans were and what his cell phone and laptop and shoulder-bag and all that, and he said it was this whole social code he had just never experienced before.

My friend is also living in an African neighborhood now, and says you can tell Africans from African-Americans on public transportation by their characteristic ways of waiting, even when clothing and looks are otherwise identical.