One evening in 1949, McNamara—head of Hamilton Credit Corporation in New York City—was dining out with two business associates. Their topic of discussion: one of McNamara’s clients, who was defaulting on a loan because he had shared his gasoline and department-store credit cards with some friends in need. Unfortunately, friends didn’t have money to pay back what they had borrowed, so good samaritan was now facing his own financial demise.

As meal ended, McNamara reached for his wallet so he could pick up check. To his horror, he realized he had left it at home—and was forced to call his wife so she could bring him cash he needed to settle tab.

This fateful meal led to an invention that has transformed how world handles money to this very day: credit card. While previously available gasoline and department-store credit cards allowed users to make purchases at a single location, McNamara’s personal plight—and that of his well-meaning client—prompted him to create a credit card that could be used in multiple venues. The Diners Club card was born. In its first year, 200,000 consumers signed up for one.

The rest is history. After carefully observing Diners Club’s success, American Express and Bank Americard (soon to be renamed VISA) followed suit. Thank McNamara next time you pay with plastic.

But has McNamara’s novel concept become more of a curse than a blessing in your life? Are your credit cards managing you—and is your debt spiraling out of control?

Here are 5 ways to tame credit card beast.

1. Know Your Limits If you have a tendency to overspend, limit your extravagances by relying on paper currency instead of plastic. Set spending limits before you leave house, whether you’re shopping for groceries or heading to mall to buy a new pair of shoes. If you find yourself reaching for your credit cards, freeze—and don’t move an inch until you can answer following questions:

• Why am I breaking my own rule?

• Am I being self-destructive with my financial health?

• Do I really need this item, or is my ability to say “charge it!” clouding my good judgment?

2. Learn from McNamara’s Client As McNamara’s client learned hard way, loaning your credit cards to even those closest to you is a surefire way to accrue debt. You are giving your spouse, children, other relatives and/or friends carte blanche to spend up a storm—and you are one who is legally obligated to pay bills that will find their way into your mailbox at end of month. Be extremely selective when passing plastic to anyone who can run up a bill—and fail to pay you back.

But have you become financially complacent, failing to consider ways to decrease your payments or overall debt?

Here are 5 secrets to paying off your mortgage in shortest possible time.

1. Get a Mortgage “Tune-Up” You take your car to your mechanic several times a year to keep it in optimum running condition. The same principle applies to your mortgage, according to Ron Chicaferro, president of Thornburg Mortgage Home Loans, based in Santa Fe, New Mexico.

“Homeowners really need to do a mortgage ‘tune-up’ at least once a quarter,” he says. “To be a savvy homeowner today means more than just locking in a low-interest rate. Borrowers need to know if they’re paying too much for security they don’t need and if their lender is charging them unnecessary fees. When it comes to saving money, it pays to know when it’s right to refinance and to ask lenders about innovative mortgage products that can reduce monthly payments. There's nothing like a mortgage tune-up to save homeowners cash.”

2. Pull Switch As interest rates rise, homeowners with adjustable-rate mortgages (ARMs)—which have become increasingly popular among consumers who want to keep monthly payments low—may want to consider switching to a fixed-rate mortgage.

“The gap between long- and short-term rates has narrowed, making even hybrid ARMs—which are fixed for an initial period—not as good a deal as they used to be,” says Valerie Patterson, senior editor of RealEstateJournal.com. “Now is a good time for homeowners with adjustable rates to consider refinancing with a fixed-rate mortgage.”

Of course, a great deal depends on how long you plan to remain in your home, as well as cost of refinancing, Patterson notes.

3. Trouble in Paradise? Money problems and debt are key contributors to today’s high divorce rate, and most families take a financial hit after a couple parts company. As lawyers jockey for position, a critical question emerges: Who gets house? (And mortgage payments…)