My suggestions...

Check reviews, do a TER search, google, and go with your gut!

If you can't find enough information on the girl and you're not comfortable, go with your gut. I am always surprised to hear how many gentlemen have had bad first experiences from rip off's or just not getting what they expected. This seems to set up a hesitation and nerves for any future encounters.
If it seems to good to be true. PLEASE do your home work. Google the name AND phone number at the very least. If it comes up with other girls names or cites. That could be a red flag.
There are also plug-in's available via this website that help filter ad's and give you info on bad numbers, rip off's etc.
Try and go with someone more obviously reputable if you can.

All in all, I think it is often a learn as you go process to find the right fit for you. But it should always be fun along the way.

OX,
Jai

I think both Layla and Jai have given some good, solid advice (I really gotta see them for a double the next time I'm in San Diego LOL!). For me, I think doing the most research as you possibly can, and listening to your gut instincts, are the way to go. I use a few ideas that have worked for me very well:
1) I don't care how good her pictures are on Eros, Cityvibe, or any other site, if she doesn't have reviews here on TER or one of the other good review sites, I pass.
2) If there are reviews, I read every one that I can. Also, the amount of reviews are important. If she has a few pages of reviews over a good period of time (say, several months to a year), I feel safer and more comfortable.
3) If she doesn't have her own web site, I also pass. Just having a phone number or email address makes me nervous.
4) I read every word on her web site, and not just the rates and stare at the pictures. I try to get a feel for their personality from their sites.
5) While all this research is great, I can't stress how important listening to your instincts are. As Jai has said, if something doesn't feel right, it probably isn't.
I'm glad you posted this, Layla. If this post, and the advice in it, helps someone have a great experience, then it was well worth it. I also have to say, even though we've never met, that you and Jai (whom I met a few times) are real credits to this community. You both look out for everyone's interests, providers and clients alike, and I, for one, want to thank you both for that. The "hobby" needs more people like you.