There is one trans*woman whom I've seen around my college campus since I was a freshman. I remember not knowing what to make of her at first, but every time I walk by her now I smile and make eye contact to acknowledge her. It's amazing because to me, even the most ordinary article of clothing looks beautiful on her.
It's because of her that I have adopted the following mentality: if I ever wonder about a person's gender, I immediately ask myself "Does it matter? Does it make them any less of a person?" And my answer to both of these questions is no.