Do you mean, what should you do for planning the trip & activities? Or how to ensure everything goes smoothly and you both get along?
I've done a few travel engagements but I no longer offer this publicly..... I'll only travel with, or to, clients with whom I have an established rapport.
If you're going to be spending multiple nights sleeping together (same room, same bed) then it's generally considered wise to do at least one overnight with that person first. If not, then you should have a very open & frank conversation as to expectations prior to your trip.
Keep in mind that in civvie relationships it is often said that you don't really know someone until you travel together.
Even if you think you're both on the same page, communication is still very important to be sure that really is the case.
Talk about how much time you expect for personal space, whether or not middle-of-the-night playtime is expected, what your usual routine is and how long it really takes you to get ready to leave the room, if you have dietary restrictions, and anything/everything about your daily life/routine or travel habits that will come into play!
As usual, I have an example from my own experiences to share: I'd been seeing a gentleman for weekly multi-hour visits for the better part of a year. He was unable to do an overnight date prior to the proposed trip, but having spent so much time together both BCD and on public dates, I thought I knew what to expect. WRONG.
The term "up my ass" doesn't even begin to describe it: he was stunned that I expected time to myself to work-out every morning as well as some privacy for daily phone calls to my children. Not to mention the fact that he was the type who likes to cuddle all night long, literally sleeping with his arms wrapped around me. He thought that was normal and expected of two people sharing a bed but I cannot sleep that way. So after a few sleepless nights I wound up on the verge of a mental breakdown, and only when I was making my flight-change arrangements to go home early did he agree to give me some space at night. But the remainder of the trip wasn't fun, and we only saw each other a couple times afterwards.
Oh, and a longtime friend/client recently asked me to accompany him on a trip for which I made a couple stipulations based upon our past experiences travelling together: I need my own room and he has to discuss choices of restaurants with me prior to making the reservations. Why? Because there were things I learned about him when travelling together that hadn't come up on overnights.
Shockingly, he still wants to take my high-maintenance ass with him. LOL.
So don't be afraid to speak up! If a client wants YOU as his travel companion, he may be far more accommodating than one might expect.