It seems as we go through life we pick up all sorts of "hints" and shorthand. Little cultural nods so to speak, that help us know seemingly at a glance what we are dealing with.
At work I'm the guy in a white dress shirt and tie, so everyone knows I'm in charge because everyone else at work dresses differently. A couple comes in my store dressed very formally on a Sunday afternoon. They've been to church. The polite and formalized discourse we have with acquaintances or people we have to deal with but don't know. Please and thank you and all that...etc
We pick up other sorts of shorthand too. We tend to be tribal in our thinking. It's a trait actually endemic to our species, so we tend to notice in-group and out-group characteristics. People that talk differently or look differently we tend to be more cautious around, and vice versa.
The thing to keep in mind is that many of these social hints we rely on make us feel certain ways, and as such we should never fully put our trust in them. To do so is to potentially make the mistake of valuing and devaluing people based on things that do not matter.
Someone recently asked me about race, insofar as it relates to dating and relationships. Now, apart from the fact that race, at least in the context it is usually presented, is a myth it is also not a personal choice. The woman that asked me this didn't get to choose to be of african descent. That choice was made by her parents. Likewise the english, french, dutch, german, cherokee, pirate, manatee, goat (I only include manatee and goat because of the pirate ancestry...you know pirates, they'll screw anything) ancestry I possess in my genetic structure was a series of choices made by all sorts of ancestors. And most of them are dead. :P
Value people for their choices and for the positive efforts they make. Do this simple thing and you'll find more value around you than you can shake a stick at.