You know those retailer come-ons promising 25 percent off your purchase if you open a store credit card? Skip them, FICO says. That's because "opening new lines of credit can hurt your credit score, and may increase your chances of paying your bill late, which can have a very negative impact your credit rating," the company notes.

While you're at it, don't run up big gift-purchase balances on the cards you do have. "Although experts agree having 3-5 credit cards helps your credit, carrying a balance leaves you with a much lower credit score, which could jeopardize your chance of getting lines of credit elsewhere," FICO says.

And it might seem like a no-brainer, but don't delay when the holiday tab comes due. "A single late payment of just 30 days can bring a credit score of 780 down 90-110 points, and a score of 680 down 60-80 points," FICO says.

The average score in Maryland is 688, a few points above the national average. (Highest? South Dakota at 710.)

Want to know more? Back in my How-to Monday days, I wrote a primer on credit scores and a how-to on improving those scores.

So are you watching your credit score? What are you doing to improve it?