Put some effort into your research and preparation - try to tip everything in favor of a good, successful experience.
Hopefully you'll enjoy it but at this stage in your life your first time might feel like more of a mission than a pleasure.
Thats fine, almost everyone is nervy about their first time and their first punt and your combining the two! Its not rocket science though and you'll muddle through
You may not need it but viagra is easily available and fairly cheap with an anonymous online prescription for a bit of performance support if your really bricking it.
Reading all the punting wikis at the bottom of the UKP home page will give you a good orientation to the game in general, and how to avoid pitfalls and get the best out of it.
Reading the reviews and regional punting board of your area will give you more of a feel as to whats available and what your attitude and expectations should realistically be (as well as being great entertainment).
Based on all that, pick an escort you really fancy the look of with reviews that show she has a good attitude to her clients, abstain from wanking for a couple of days before the meet, scrub yourself up, be polite, calm and friendly but assertive about what you want and get the job done.
good luck to ya