Try to find someone who is a safe bet who is very active on Adultwork, with good feedbacks and also has excellent reviews on here.
If you do book someone, be up front and tell them it`s your first time because no doubt you may be a bit nervous and a good girl will be able to make you relax a bit and she will do her best to make sure you enjoy your time there, it`s in her best interests, because if you leave happy, she hope`s you go back.
You may want to go back a couple of times to get the hang of it all before expanding a bit and start booking other girls with a bit more confidence.
The last thing you want is ending up with some silly girl who takes the piss because that will put you off punting, try someone who is a few years older who will probably have a more mature outlook on meeting first timers.