Not Like I Care
I generally don't care which way people go. But I have always had a knack for knowing. It isn't just stereotypes either. I've known people that had none of the stereotypical behaviors, but I knew. I know when people are bi - or even just a little bi. It has helped me a great deal with my students.
I can be wrong - but it doesn't seem to happen often. I think it has something to do with the fact that I am considered an empath.
I don't really see how it is important who people are sexually attracted to though - so I'm not sure the skill is of much use, except for helping some of my kids deal with it when they discover their sexuality on their own and freak out.
It drives me INSANE when I can't get a read on someone.