Are you getting ready to welcome friends or relatives from overseas for the holidays? Or perhaps you are one of those visitors. This might be a good time to check the latest U.S. entry requirements, especially if you or your guests are traveling without a visa.

Most citizens of the 34 countries participating in the so-called visa-waiver program think that all they need to board a plane to the United States is a passport and an airline ticket. For the most part, they are right. But what kind of passport and ticket? If your passport was issued before Oct. 26, 2005, it must be machine-readable, with a strip at the bottom of the title page that can be read by a computer when swiped…