If Your Card is Stolen
The faster you act to report a stolen card, the more likely you are to minimize problems. The first thing to do is notify the issuer immediately, especially if you're in a foreign country.
Also, if you carry multiple credit cards, you may want to sign up with a card registration service. In the event your wallet gets stolen, the service will immediately contact all of the issuers for you.
A helpful hint: If you're traveling on vacation with your spouse, each of you should have a credit card from a separate account (many spouses share credit card accounts.) That way, if either of your wallets is stolen, you don't end up cancelling all of your spouse's cards when you report the theft to your issuers. This will leave you at least one active card while you're traveling.