How do you size up people?

Humans have always been told first impressions count.  Do we lay too much weight on this statement?
I know from personal experience that I have been wrong on occasion about people, I have also
apologized to them when I was wrong about them. One person in particular comes to mind, a
friend of mine that when I first met him I thought he was full of himself, completely self
centered and totally clueless. I could have not been more wrong, he is a  genuinely kind person
that is a wonderful father.
I would say that most of the time I am right, but I am not so sure it is about first impression, but
more about listening to your gut. And this should be taught at a very young age.  I would always observe my daughter as a child and her gut was right on most of the time with most of the people,
why, because they have no filters, do not know what "judgmental" is for the most part.
I can think of thousands of people that have read me wrong, for many reasons, my question is it because of our facade or because that are already sizing you up by the type of the clothes you wear,
the car you drive or the home you live in?

I remember I was at lunch with a guy and an ex-boyfriend walked in to the restaurant, he saw me
having lunch with the guy and he said hello and called me the next day and asked me "what the
hell are you doing dating that guy?" I said why, I really did not know him that well yet, and my
ex said to me, not my business but you are not the type of woman that would go out with him, he
said just watch the way he treats people and I did and my ex was right and I left him.

Finally my last little story, I went to a Reiki treatment:

Reiki is a Japanese technique for stress reduction and relaxation that also promotes healing. It is administered by "laying on hands" and is based on the idea that an unseen "life force energy" flows through us and is what causes us to be alive. If one's "life force energy" is low, then we are more likely to get sick or feel stress, and if it is high, we are more capable of being happy and healthy

For me it was cathartic, as I was laying on the table and this beautiful woman was passing her hands
over me, she starting telling me her story, and at the end she said. "I live my life and I fall in love with the soul of the person, not the gender". She said I am currently married with a child, but it
does not mean that I could not fall in love with a woman, because she sees the essence of the
person and not the carriage. From that day on I view love differently, because now my love
cannot be identified by the love of a child, parent or spouse. Love is love! And what is "being in
Love all about" that to me is not a real love, it is a transitional emotion confused with the word
love.
More on that next time.