Isn't it funny how you can form an opinion of someone based on really nothing at all?
Every day on my way to the bus stop, I walk past Jim. I know nothing about him other than that he is older (based on the white hair and beard), he has a routine that sends him walking up the hill every afternoon as I am walking down the hill, and apparently his name is Jim (based on the name stitched on the work shirts he always wears). So I don't know anything about him, but I like him. When we pass every day, he smiles and nods. Sometimes he says hello. So he seems nice and I enjoy seeing him.
On the other hand, there's a lady at my bus stop that I also see every day. I'll usually nod or say hello when I walk up, and she sometimes nods back, sometimes just kind of looks away as I walk up. So even though I know nothing about her, I kind of don't like her. She's probably a really nice person. Maybe she's just tired at the end of the day. Maybe she's shy.
I guess what I'm getting out of this is that I should take the trouble to smile and say hello when I see someone... otherwise maybe they'll decide to dislike me for no good reason. =)