What attracts me first: Hardly ever an ad--I rarely look at the ads. Usually what a lady has to say on boards or P411, etc. I want to have a sense that there is an interesting personality hiding under the pictures--someone I will enjoy spending a few hours with at dinner and between active engagements.
Next: A web site that conveys creativity, sensuality, and gives me a sense that she enjoys her time. Cookie cutter sites and ones with bad communication skills are a big negative.
If I get past those, then it is physical interest (almost never a problem), price, availability where I will be.
Then how she responds to my e-mail or PM clinches it or not.