Make sure your passport is valid before heading on a cruise. (Photo by yenwen/Getty Images) Long before you check in for your cruise, you should take a quick glance at whatever identification document you’re going to use during the check-in process to make sure it hasn’t expired — or is even close to expiring. On many cruise itineraries, you will need a passport, and many of the countries that cruise lines visit require passports to be valid for at least six months beyond the date you plan to leave the country. Also, note that many countries require you to have at least two blank pages ...