As a newer provider I wanted to pick your brain a bit to see what really makes you personally - not to generalize - tick.  

Also providers what do you believe is the biggest factor? is it your pictures? twitter? reviews?

I'd love to get your feedback!

1, 1a, & 1b = Young, Thin & Pretty!

Pictures > Reviews >>>>>>>>> Twitter.

pretty face
loves to kiss
$ reasonable $350
and location!

ok thats interesting

how do you determine if they block their face?

ok thats a good list

I block my face like many others so how do you determine who is pretty?

That's a good question.
First step is to....go to the reviews!
But if none exist, and she is claiming to be young (25 & under) and thin, then I would most likely to be willing to TOFTT. Have done this plenty of times in the past. Some good, some not so good. Last summer I called one from backpage who claimed to be young, thin & pretty. But when I met her she was not particularly young (probably under 30 though), flabby, and the face was about a 5. I had her give me an HJ, BS'd for a while, a second HJ, and then left, never to return. It happens..

For me
1. Looks
2. Reviews
3. Menu
4. Cost
    Sometimes with a blurred face picture you can get a sense of what they look like and are willing to take a chance. If there are reviews they will typically mention the looks and you can judge by their other reviews of what they consider pretty.
    The reviews even if it is only one will give a sense of what the provider is like and again you can get a feel by the reviewers other reviews
   The menu is important to me so if there is something I am looking for and it is not on the menu I will move on.
   Cost is always a factor as most everyone has a budget while looking for the most bang for the buck

Note: The following are not in any kind of order.  In fact, the first way to get to see me is to be recommended by someone I know and trust.

1. Location - I am on Long Island, while I can and have seen providers in Manhattan, if they are closer to me, it makes it easier.
2. Availability - I have a small window of "playtime" during the week.  Basically only on Fridays during the daytime.  
3.  Beauty - duh.  Accurate pictures on p411 or her own website
4.  Price - I'm on a budget and cannot see 600 or more/hr people, just not happening
5. Service/reviews - here on TER.  If you have consistent scores and the majority of your reviews are great I overlook the outliers.
6. If we click I will see you again, and again.

1. Ethnicity - open to all but depends on my specific mood that day
2. Location - easy access by private or public transportation  
3. Service provided - Depends on specific mood..Usually FS but sometimes looking for less
4. Novelty - am I looking to try out something new that day
5. Personality / attitude of provider - self-evident..
6. Cost - service provided commensurate donation

thanks for the reply!

thanks for the reply! I gotta make sure I keep my score up!

Hmmm cost is last - thats interesting! Ethnicity is out of my control lol

I would also add responsiveness to messages. I usually look for that in the reviews I read. The more responsive a provider is, the better

I agree as a new provider I always answer my emails immediately but I am guessing as demand goes up some providers don't have the eagerness

Like many of the previous answers, my choices depend on the situation. I hobby only when traveling, so schedule matters. Because of where I stay, outcall often isn't an option, so in-call capability helps. Body build is important -- there is no single right answer, but sometimes I'm more interested in one look or another. Reviews matter -- both for a sense of menu and for a sense of what leads to good connection. (I'm getting up there in years, so I like to see that someone is comfortable with older men.) I definitely respond to well-written ads or web text, especially text that isn't just one more "here I am, I'm pretty, I like what I do, I want our time together to be special" blah blah blah. Given all those filters, I've accepted that although cost is an issue, sometimes I'll have to stretch if everything else looks right.

So the answer is: It all depends. Not very helpful, I suspect

you read the reviews

you trust your muse!  Maybe you reach out and ask?

Ask if they are beautiful, ask if they love to kiss, if they (like me) have incredibly high level of hygiene...

well, with some gorgeous babes,  they show a little bit of their face.  Like in your case, we see some luscious lips...!  I imagine they are on a gorgeous face!  Am i correct?