Hey TW,
First, I'd like to think that you should choose any method of communication you are comfortable with is what you choose. Some people only prefer to use email others text voice. As a general rule, you should be conscious about the implications of using your real name with people you don't know (so that doesn't just apply to "hobbying").
Personally, I use a separate line and phone. Try not to use disposable numbers, as they are somewhat detectable by agencies and SPs and they might not even respond. Also using the same number will make it easier to establish a relationship with who you are calling which can have many benefits down the line.
I also created a separate google profile to use for my browsing and for emails which makes it easier for me to remove any traces on my computer.
Whomever you contact can answer any questions you have. But since most of the information is available on their sites or this board, I'd suggest not wasting time asking questions they get a billion times a day. So when you call just discuss the time and place and be there when she comes or be there on time if you're going for an incall.
It can be different for everyone, but I'd say a typical meeting will start with a rush as the moment gets closer... Whenever I meet a courtesan for the first time, I try to make her as comfortable as possible. Don't forget she's walking into a strangers home or room. When I open the door I want to make sure the rooms are well lit and I don't hide behind the door. She should be somewhat comfortable walking in... but when you go to an incall don't be surprised if she's hiding behind the door. Remember that they will most often be wearing very sexy outfits and probably don't want to be exposing themselves or what they do to a passerby in the hall.
In the case where you're really not comfortable with the girl (incall or outcall), this is the best time to cancel. No need to invent a story of how you forgot your wallet in the car. Just say sorry and leave quickly. In some cases, some people do expect at least a 20$ to pay for the driver... but that's on a case by case basis, and you can even discuss that at the moment of booking. But honestly, if you did your research, there should be no need to back away. I'd say the general rule of thumb is the moment you've unwrapped her, you're accepting the terms. However I did once have a situation where the girl had a great attitude, cute face, but when she got undressed, she unfortunately had a lot of stretch marks and very different breasts due to having kids. She had photoshopped her pics. I felt bad, but discussed it with her as I knew the session wasn't going to be what I had in mind. It was hard for me as she really was a sweet girl. I gave her 40-60$ and she accepted the cancellation. But not all girls as this cooperative... again your homework will prevent that when done right.
Last note, when paying the girl, its usually proper etiquette to pay at the start of the encounter. You will read a lot of posts about how guys hate to pay at the beginning etc... as previously mentioned, I like to make the girl comfortable. So making sure she knows she isn't going to get scammed is a good thing. If you're worried about getting scammed yourself, just make sure the $ doesn't leave your room or home. So never accept that a girl leave for a few minutes with the money to pay someone else or that she forgot something in the car. Reputable girls and agencies will never request that. I usually just confirm the amount and leave it visible; they usually leave it there until get cleaned up.