my biggest turn on, as simple as it sounds, would have to be when a girl dresses sexy. it's just good to know that a girl is trying to be as sexy as she can just for you.
sexy panties are a huge turn on, especially thongs. i'm a fan of the "whale tail" look (you know, thong hanging out of pants kind of like a whale's tail out of the water). or even better - a skirt with no panties.......so hot
i have a thing for school girl outfits and i also have an attraction to goth and/or punkish girls. peircings are really sexy. my favourites being belly button and clit.
that's all i can think of for now, i'll come up with more later.