Done this a few times......
Setup a few sessions ahead of time. Not just meet at an incall and fucking but a dinner date etc. You will want to make sure you are comfortable with each other intimately, but also casually.
Things to look for in my experience.... how they behave in a social setting, how they dress and carry themselves that kind of thing and how they treat and react to those providing services. You do not want a Drama Diva harassing peeps at resturants, on planes etc... it makes traveling with them less than relaxing
You also want to get prices and expectations squared away ahead of time... from my experience you'll find those who will want the experience just for the experience to those who will do weekly rates etc... the whole gambit. Just choose which you are comfy with and go from there.
You'll also want to make sure there will not be any issues with traveling, for example if your going to another country make sure they have passports and can travel etc.
Know what activities you will want to do ahead of time and try to find someone who shares desire to do them, like golfing, fishing, hiking, scuba or snorkeling etc depending on your destination. Helps if you plan things out ahead of time with them so they feel part of the experience not just an add-on or tag along.