When I used to go on vacation, albeit many years ago, preparations included making sure the travel documents such as passports, visas, tickets, etc. (almost all my vacations entailed international travel) were in good order, vaccinations, if any, were current, travellers' checks were bought, flights were booked and double/triple checked, suitcases were packed and weighed and packed again!
Most of my vacations, back then, were trips back to the country of my birth, so, there were lots of gifts to buy for family and friends. Shopping early with a list of everyone plus several extra "all purpose" gifts was the rule. Plus we have a custom of taking parcels back for everybody else's family and friends, too! So, generally, one suitcase of things for one's own family and friends, another suitcase of things for other people's family and friends!
Trip planning included making arrangements to get to the airport at this end and being met at the airport, upon arrival. Airport shuttle services are indispensable.
It used to be a long flight (approx. 23 hrs!) with one or two stops en route; I used to take things to do in flight, while waiting in transit, etc. Back then, knitting needles and sewing kits were allowed in the cabin. These days, I think a paperback book or two would be better.