First of course the lady's photos have to attract me. I like different body types faces and hair depending on my mood but if the photos areas obscure as a Fellini film tthen I'm unlikely to get interested. I need to see what you look like. That's the hook.
Reviews--not just scores--are next up. The hottest looking chica won't excite me if the substance of her reviews tell me she's not into what she's doing.  Specialties are nice but better to do what you like and do it well instead of doing stuff you're just not into.
I have the good fortune to be able to hobby pretty often but I'm not into spending just to spend. I have a budget that I stick to and while I would never try to bargain a lady down I'm going to stick my budget.  So price matters.
And lastly a combination of location and hassle factor. With so many lovely ladies to choose from and my own well being and happiness to consider I do think about how far I have to go, whether the lady only does appointments at a certain time and whether I have to get a room because she doesn't have incall.  Of course for the right lady I'll drive through LA rush hour traffic and pay for a room at the Ritz. You know who you are.