What is the proper protocol to find out info on a provider's rates and/or services if there is nothing in their posted ad? When do you ask a provider for this info? Do you ask them through email, ask them when you call them about setting up an appointment, or do you discuss the services when they arrive for the appointment?

Have you checked her website & TER profile as well? If it's not in her original ad, you'll usually find it in one of these 2 places. If all else fails, I'd say e-mail, as many are touchy about $ conversation over the phone... and don't wait until the scheduled appointment.. too many variables.. what if it's too much, then what? And many ladies will walk out on you/ask you to leave, if you ask the donation once you've arrived/they've arrived.

It would leave too many chances for an unpleasant surprise, misunderstanding or setting a bad tone for what follows. You want to start things off with a kiss at the door as you smoothly place the donation on the dresser, not a discussion of the amount.

There shouldn't be any problem with asking in email or over the phone about her rates for her time. That's perfectly legal and discreet, however many escorts get suspicious, so be sure you've checked every other possible place online before resorting to that. And be aware that the rates in her TER profile may be outdated.

but do not discuss what you get for it.  Just rate per hour for appointment.  It should be clear from reviews what is included.  
You really need VIP to read the reviews.  The mere existance of reviews does not mean they are good.  Even those with "Stay Away" reviews will post a link...  figuring most guys are too cheap to get even 1 month's VIP to check.  This is FALSE ECONOMY...  VIP costs less than a spoiled date or wsted opportunity.
Newbies should stick with well reviewed providers...

Am assuming you are looking at ads on BP. Read ad very carefully. If rates are not in ad and whether or incall/outcall are both available, call and indicate you saw her ad on BP and you would like more information about her "SERVICES".  Do not use term "rates" but rather - "donation". Lots of providers do not response with their prices if the term "rates" is used. Also inquire if the "donation" is the same for incall and outcall also can ask if 30 min sessions are offerred. Do not ask any other questions related to "services' . Thank her and hang-up. If interested, call back in 15 minutes (will give you time to think over info given) and make appointment.