You already know a lot about credit cards. You’ve heard that consumer debt in this country-particularly credit-card debt-is at an all-time high, while our savings rate is lower than ever before. You realize that the boom in online shopping, with its absolute dependence on credit cards, is further fueling their use. You are well aware that running a balance on your plastic-and paying the unconscionable interest rates that come with it-is one of our most basic and widespread financial blunders. And you suspect that the sheer volume of direct-mail credit-card solicitations with low teaser rates must be devastating the forests of northern Idaho.
Still, credit cards are a fact of 21st century life, and it only makes sense to understand how to use them wisely. While it’s probably impractical to keep all plastic out of your wallet, it is prudent to limit the number of cards you have, and, of course, to pay all balances in full every month. Indeed, having only a traditional American Express card, which doesn’t allow you to carry a balance, can be an excellent way to impose fiscal discipline on you and your family-although, as the Visa ads point out, not...