Equifax has an excellent webpage on avoiding and remedying identity theft. TransUnion also has a convenient list of contacts for reporting fraud. Below is a short summary of the information from Equifax.
Be prepared:
To help minimize and resolve identity theft if your wallet or purse is lost or stolen:
As of April 15, 2003, you can have a two-year fraud alert placed on your account with each organization by calling just one of them. They will also put you on a two-year opt-out list for credit and insurance pre-screening. You will also receive a credit report from each of them. Be sure to look at each report carefully, as the three organizations share very little information with each other.
Before April 15, 2003, you had to call each credit organization separately, the fraud alert policies varied (e.g., 90 days for Experian, 12 months for Trans-Union), and Experian didn't automatically put you on the opt-out list. Of course, you can always sign up for the opt-out list at any time, but it's nice that they do it automatically, now, as part of your report of identity theft.
If you believe identity theft has already occurred:
The Motley Fool has an excellent article that tells the story of one of the victims of the big identity theft racket that was busted in the summer of 2002. The article includes some good tips on protecting your identity.
American Express Private Payments allows you to charge purchases to your American Express account without revealing your actual account number. You use the Private Payments service to generate single use numbers that appear to the vendor as an American Express account number. When the vendor submits the charge, American Express maps that number to your real account. Not only do you not have to worry about the vendor accidentally exposing your credit card number to the Internet or getting hacked, you don't have to worry about an employee or anyone else reusing your credit card number for additional purchases.
With certain Visa cards (it depends on the issuing institution), a program from Visa called Verified by Visa allows you to add a level of password protection to some of your online purchases. If you shop online with a supporting vendor, you will be prompted for the additional password you set up for your Visa card when you complete your purchase.
However, recent studies cast doubt on Verified by Visa and MasterCard SecureCode. The way they are integrated into websites is frequently done in a very insecure manner. Also, it seems the main result is to pass responsibility from Visa or MasterCard onto the customer. While relatively easy to hack, they maintain it is secure, so if a purchase was made with your code, they are allegedly more agressive about making you pay for it.