One way of learning about your orientation is to compare your reaction to supposedly-sexy scenes to other people's reactions.

I was thinking about the movie "Who Framed Roger Rabbit" recently, and thought back to Jessica Rabbit's introductory scene.  I remember seeing the scene and realizing that it was supposed to arouse the audience.  I felt upset with the moviemakers for so blatantly trying use sexual arousal to try to get more sales.  I didn't feel any sexual urges from that scene, though that may have been because I was only 11.