They all do things a little differently but in the end its all pretty much the same format. They have people that handle their DMs for them and attempt to get you to spill all kinds of personal information about yourself, like name, where youre from, hobbies, and so on, trying to build some kind of personal relationship for obvious reasons. Then depending on what they have available, they start out with relatively cheaper, non-explicit sets, eventually raising the price to the max allowed by OF and what they sell is supposed to get more explicit PPVs. Theres usually some kind of story with each of them that they make up on the fly, but you see it a few times, and you get the idea fast.
Most of the time, they have the girl film some stuff, and they chop up each vid into shorter clips and increase the price on them until you get to the end of what is basically a few minutes of a single video. Sometimes there are pics with it or else they will just save video frames and make it seem like you are getting more, but you wont know until you open it. As I said, they arent all like this, but the ones that usually are just yapping on CB and doing nothing but trying to get people to go to their OF for everything else are the ones to watch out for.
It doesnt mean you cant get what you may be looking for, but its time intensive and usually underwhelming and a big waste of time and money for what it is. If they offer custom stuff, you have to tread carefully because its rare that ever gets done and costs a small fortune, and since its never her you are dealing with, you are most likely to get ripped off sooner than later.