Whether you left school before Eisenhower became president or received your diploma yesterday, you're always being graded on how you handle credit. What's more, the score you get--a number ranging from 300 to 850--is no trifling matter. That number (known as the Fair Isaac Corporation or FICO score, named for the analytical company that devised it) determines the rates you get on your mortgage and car loans, even whether you are approved for a new apartment.

For instance, say a score of 650 gets you a mortgage rate of about 7.9 percent. Boost your score to 750 and you could qualify for an interest rate that's 1 or even 2 percentage points lower, saving thousands over the life of a 30-year, fixed-rate loan. That's enough to make even a back-of-the-class slacker pay attention. Yet many consumers don't know their score. And some people--particularly older women--don't even have a FICO score, typically because their mortgage and credit cards are in the name of their spouses.

"But all marriages end, even the happy ones," points out Ginita Wall, director of the Women's Institute for Financial Education (www.wife.org) and coauthor of It's More Than Money, It's Your Life. "And if a woman does not have credit in her name, she is going to have problems." For instance, if she wants to start a business later in life or simply open a department store charge account, she needs to show that she handles credit well. Without a good FICO score, lenders tend to be skittish about extending credit.