You booked the flight and hotel months ago. You made tour and dinner reservations a few weeks ago. What other details should you take care of in advance of your international vacation?
Call your credit card company to notify them you will be leaving the country. It's no fun when they freeze your card to prevent fraud but then you can't use it either.
I always recommend that you bring a different card from your traveling companion. If one of you loses your wallet and has to cancel/freeze the cards, people often forget that means that the card they share with their family member will be shutdown as well. You can both bring the card you plan to use for most of the trip but make sure that you each have a card that the other does not have in their wallet.
Make sure your passport is valid for 6 months after the end of your trip. People often check that their passport hasn't expired but don't realize that many countries require that a passport be valid for 6 months after the final day of the trip. Airlines or customs can refuse boarding or entry to a country because of this. Even worse, This isn't covered by basic travel insurance. Speaking of...
Okay. This is something you should invest in when you put down your deposit. Note that you can always increase plans to cover the cost of your trip as it grows but I'd hate to lose that deposit. One of the big factors I stress is the medical coverage you get with these plans. Our regular US medical plans claim to work overseas but often don't. Plus, the peace of mind insurance provides makes it easy to tackle minor problems (and keeping them from becoming major ones) is well worth the cost.
VISA AND VACCINATIONS
Find out the entry requirements for the country you are visiting (or sometimes even where you have a layover). You can easily search the State Department website by country. While many are easily obtained on arrival or online, some visas can take a while. Therefore, find out the details when booking your trip and not 2 days before you leave on the trip. Those last minute rush fees (if possible to execute) are brutal! Also check out your destination country's requirements for vaccinations. Some may require proof and some may require a few weeks notice before becoming affective. This too can be found in the country information section of the State Department website.
These little things can ruin a trip if not done right so make sure you're prepped and ready to relax!