I tend to be a very bad initial judge of character.
On the first day of my acting class, there was one girl who always raised her hand for every question and answered with a solemn face. She was an acting major in a class for non-majors. I automatically assumed she was a pretentious know-it-all who was in the class to be better than everyone else. I soon found out that this girl would smile at everything and encourage everyone to be better. She just has that solemn, cool and collective face when answering questions.
I saw a man sitting by himself at a bus stop once. Everyone else waiting for the bus waited outside of the little shelter. The man looked like a bum, but looked like a nice man. I sat next to him at the shelter and he immediately asked me for change. I politely told him I had none. He then asked me for a cigarette, to which I also said I didn't have. He then apologized and proceeded to mutter something every time someone walked by. It was usually a quiet holler at every female that walked by or a derogatory remark to every guy. In short, this man was an asshole.
When I first see someone, it's like I'm given a multiple choice of their personality and I always get it wrong. Good thing I always get second and third chances to reevaluate people I actually want to continue talking to.