Not very. And actual sexual attraction is pretty inexplicable. Like on the bus today, I sat in front of an Asian girl, I never find them attractive, but today I felt like turning around and, well honestly, pulling her panties down and eating her out. I think it had something to do with her sitting on a seat above the wheel well, which meant she was elevated.. meaning my head was like at her crotch height, and her pheromones were leaking out or something. I make it sound so crude. I never even got a full look at her, I was just aware of her.
As far as crush-style attraction, it's a pretty pair of dark brown eyes.
Also, chicks with dirty mouths are always a turn on, same with girls that moan a lot, (they are rare, but they happen), and girls that take their shoes off and/or rotate their ankles.