If you plan on doing any overseas traveling…make sure you call your credit card company BEFORE you go. The main reason to call is to alert them to the fact that there will be charges coming from outside of the country. With identity theft so rampant, a lot of credit card companies proactively work to combat it by blocking transactions they think are unauthorized.
If your credit card company knows you live in Cincinnati, Ohio and you're suddenly making purchases in Florence, Italy, there's a high probability that your card will be denied until they can establish that it hasn't been stolen.
Many travelers rely heavily on credit cards, so save yourself the trouble and embarrassment and call your credit card company in advance.