Whatever you decide to do, make sure that you confirm a few days before, then the day before an afternoon appointment (or maybe morning of an evening appointment).  Not to pester them.  Just a quick, "hey, want to make sure we are still on for..."  Can't hurt to slip in a compliment about one of their pictures, or outfit, or something.  

Appointments slip through the cracks all the time, they forget to write it down, or they don't write them down, or they just plain forget.  After all, we get appointment reminders in the real world all the time,  I just got one from my dentist.

I normally like to schedule my dates about a week in advance.  That way I feel I have a better chance at getting the time and day that I want.  Don't like same day appts at all.  I wouldn't think that a week is too far in advance, and no provider has ever complained about it.

Swim

so there's no ideal amount of advance notice. Since the saying "the customer is always right" to some degree works in the hobby, book according to your schedule. I'm a planner so I book in advance anywhere from a day to a month, just depends on my travel  and appointment schedule.  

So it is easy for me to predict what I will be doing for the next three months at least, unless there is an emergency situation. I usually like to get the screening portion out of the way and then make the appointment, confirm a week before and the day before although it is nice to establish a good rapport with the gentleman from day one, perhaps a quick email within time to time is not annoying

I generally like a week, but can do 2-3 days. It's not my schedule per se, but screening and securing an incall that take more time. Most women are happy to prescreen for a meeting in the future.

ask the provider you have decided to see. All of us are so different with the way we schedule. Sometimes  screening can be done in just a day, but that's not a promise cuz the provider your trying to schedule with might not even be able to get back to you until the next day. I don't schedule but one or 2 ppl a day & not everday either. So once verified, you might be able to call me & get the appt. same day, but then again I could already be booked for the next 3 days.  
Most important thing, is to make sure you get advance approval that you want a 2hour appt. I had someone show up & get pissed cuz they wanted a 2 hour appt. which wud have been fine if they wudn't have been 45 minutes late cuz I try to schedule leaving at least an hour in between appts (due to time going over, shower, cleaning up the place,etc....) But if they would have told me ahead of time we could have made it happen.....