at the first sight you decide if this woman is sexy in your book or not, then after that her style, way of talking, way of thinking.. etc either support your opinion or destroy it!!.. for me the sexiest women i have met were very sexy to me at the very first sight!!.. other girls i didnt see sexy at the first sight then their "way" made me see them sexy but still not as sexy as those i find sexy from the beginning!!..
Sexy is not a Look, get that through your head. Sexy has more to do with their attitude, demeanor. A retty woman can have a bad attitude or be whorish, and and be a total turn off. A normal looking woman can have a sexy demeanor--attitude, in a sense, she is sensual, it is natural for her. That is why many dudes go crazy for Brazilian women, or latin women in general. They tend to have a certain sensual-ness about them, that is natural.
At first sight I see a woman with too much make up (wonder what her face looks like without all that makeup), a man face, and her face leads me to think that her body is

. She looks like someone's mother---don't tell me you have a Oedipus Complex. Now if you see the pics of the other arab women, they have a natural look, if they are wearing make up, it's not much.
Bottom line, you can't see "sexy" at first sight, "sexy" is the experience you get from her, by observing her, talking to her, her tone, the way she licks her lips, twirls her hair, interacting with her. How she interacts with you is what really determines her "sexiness".