To start with somewhat of a broad generalization... In the hobby, I've observed that there are two general price points. There's the $300 and up world and the lower priced world that generally has prices in the $150 to $250 range. My budget puts me into the lower price group, and although I have some favorite providers who I meet over and over, I like to meet new providers. Lastly, I generally schedule for the same day. Note that I think many of the reviewers on the site are in the $300 and up range and plan ahead more, so they likely have a very different process.
For me it's like this.
I look first on RoomServiceGirls.com because they bring great talent at an affordable price. If I can see one of my favorites there like Charlotte (my very favorite) of Daphne or Sarah then I'm all set. My only issue with Room Service is that their geographic sweet spot is more north and west of what is most convenient for me.
I then will take a look on BostonAsianDolls.com who are on the more expensive side of my price range, but I've had some great experiences with them and see a lot of their talent.
I do have some favorites in the more expensive group (like Angel Exotic), and will sometimes try.
Then I look at backpage. There's a lot of crap out there, but it's usually easy to tell. I usually take a quick glance and then search by town. If I find a favorite, great... Otherwise I'll see if something catches my eye and will google the number to hopefully find a review here on TER, or alternatively start to convince myself that it's a legit ad (which often takes weeks).
If I can't find a connection through these methods, I either give up, drive to providence for a spa or strip club.
Like I said, my process is likely to be different than many other people.