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Search reviews for the criteria that you find attractive.  Take the time to read the reviews, you will learn much about her likes and dislikes which is key to intimacy (unless you are just looking for the proverbial quick fuck, in which case yes just call).  Don't hesitate to PM a couple of guys who have reviewed her, back channel communication seals many more deals one way or the other than people talk about.  Guys can communicate openly without having to worry about the provider throwing a  shit fit and blacklisting him.  

PM the ladies that you like after all that, introduce yourself, what led you to the hobby. what you like in a date, what you dislike if you wish.  Establish compatibility, it is so important to the experience.  Introduce yourself and flirt and let her get to know you a little.  It goes a long, long ways in your favor (and ultimately hers).  

Make sure the agency knows that you plan to use them as a reference, common courtesy.  Don't be surprised if welll reviewed providers will not accept that as your only reference, you are on your way but not "there' you need to keep building your resume.  This will sometimes mean seeing a provider further down your list than you prefer, just treat her like she was your first choice anyway, uber-respectful of her and her body and emotions at all times, pamper her, and she will show you just as great a time as your first choice and she will become the next level of reference for you.

And remember you are doing this because it is fun, there will be frustrating moments and they are part of the process.  If someone is a dick or a bitch to you, further proof of what you already knew.  "Buzzkills are everywhere".  This hobby REQUIRES a thick skin at times.

When you find "that one", the provider who is giving you whatever it turns out you came here for (ATF) and (hint:  it may be different than what you thought), tell her.  Reinforce that she what she is doing for you is what you need, that she got it right, and treat her well not just physically and emotionally (which you should be doing anyway) but financially.  Remember she is doing this for her own reasons, and it willnever be because your dick tastes like ice cream and you are the best lover ever.  Don't be too quick to settle on an ATF.  see at least a half dozen women, have different experiences.

And keep comimg out here and learning from other's successes and mistakes.  It is like golf, none of us ever masters this hobby you just establish increasing comfort levels.

(diatribe off)