With a "thin file," you have credit -- just not much of it.

"You're in there and you have some data," says Tescher. "But you don't have enough trade lines to be automatically scored. And it usually means less than three trade lines (or accounts)."

One solution to build credit: a secured credit card.

Beware of "fee-harvester cards," says Linda Sherry, director of national priorities for Consumer Action. These cards charge fees for everything, and those fees are high, she says.

One good source for a secured card is your bank or credit union. "Many banks don't necessarily advertise these products, but they have them," says Tescher.

Make sure you opt for a credit card that reports your on-time payments to the three major credit bureaus -- Equifax, Experian and TransUnion. Some cards don't report or only report if the account goes into collections.

If you're looking to build good credit, you need a credit card that will tell the bureaus all about your good habits.