I am with Sylvester here. I much prefer longer bookings, but obviously that comes at a cost, and if you prefer long bookings, you can't punt as much.
I think that more important than the girl's attitude is your own. If it is your first time, do you just want to get it over and done with, or do you think you will be nervous or whatever and need longer to feel comfortable? The important thing to remember (and as a first timer it can be difficult) is that you are just as much responsible for setting the pace as the girl is (and remember that not every girl is out to waste your time). If you think it's time to move things on, then say so. I like to have a bit of a chat over a drink at the beginning, but after the first few minutes, if I think it is time to progress matters, it's easily done - just something like 'shall we go through to the bedroom now' tends to do it.
I agree with the majority on overnights. I have done a few, all have been poor value compared with shorter daytime bookings, and a fair proportion have just been bad from all perspectives - value, sex and satisfaction. I think most girls see them as maximum money for minimum effort. If you find a good girl who you like for a shorter booking, it's worth thinking about booking an overnight later - but don't kid yourself, you won't be fucking her all night long, and she will be gone as soon as is reasonable first thing in the morning. A chunk of your money will effectively be spent asleep.
It is definitely worth setting out your expectations to the girl before you meet. If there is any reason to think she is a time waster, you are likely to start seeing warning signs before you actually meet, which will save you money in the long run.
Whatever you decide to do, best of luck - and most of all, enjoy yourself!