I have actually written about this in the past – about 7 years ago – I’ll link it here. I do want to highlight this paragraph as this paragraph pretty much answers this question:
I often believe I have a pretty good judge of character when it comes to people though I would never say it to that individual’s face because that would be judging people. I can typically read an individual like a book by observing that person’s behavior or through interacting with this person. You see, the action, speech, and appearance of a person can say a lot about that person.

I just want to point out that I have been wrong before and being a “good judge of character” does not mean I go around judging people. I wish I was that brave but I’m not that kind of person. Knowing these things about a person will merely give me information of whether or not I want to continue a conversation with this individual or walk away. I don’t think anyone should have the right to judge another person’s character, only God has such right.
I think it’s the reason why it peeves me so much when I see another person judging a person based on his/her appearance. A lot of the times, how a person dresses does not define that’s who he/she is.
Take me, for example, my mom has always called me “sloppy” but really, it’s because it’s very hard for me to find something that fits me.
So, see, even a keen observer might be getting me wrong. My point is use people’s character as a reference point and not as something to judge.
