For one thing, multiple inquiries from lenders for your credit reports in a short period can trim your score, especially if you don't have many credit accounts or you have a short credit history. Why? FICO says that people with six or more credit inquiries on their reports in a short period are eight times more likely to declare bankruptcy than those with no inquiries.

What could be more damaging to your score is how much you charge to your new cards. If your balances are near the cards' limits, you'll likely increase your credit-utilization ratio -- the amount of debt you have relative to your credit limits. The higher your ratio, the greater the negative impact on your score. If you don’t charge a lot on the cards, you pay them off quickly and you keep balances low, your score could eventually benefit from the higher credit limits. But in general, you should take on credit sparingly.

Your spouse's score alone won't affect yours, and vice-versa. But if you take on a loan or open credit cards together, or if you put your name on any of your spouse's accounts, you're both responsible for the debt. As long as you make payments for any joint accounts on time and don’t load up with too much debt, your credit score should stay high.

It's true that the age of your accounts is included in your score and that the existence of older accounts has a positive effect. But even after you close an account, it continues to be included in the age calculation. Your score could drop, however, if closing the account boosts your credit-utilization ratio. And if you open a new credit card, the average age of your accounts could drop.

Library fines, parking and speeding tickets, and other obligations to the government left unpaid won't go directly to your credit report. But if they are eventually reported to a collection agency, they could damage your score. That goes for anything that could go to collections, such as unpaid rent and medical bills. And even if you pay up, collections will appear on your report for seven years.

If you're applying for credit cards, inquiries from several lenders at once can ding your score. But you have 30 days to shop for mortgages, student loans and auto loans with no effect on your FICO score. And under FICO's newest scoring formula, all inquiries for one of those types of loans within 45 days of each other are counted as a single inquiry

A request to check your own score is classified as a soft inquiry, and it has no bearing on your score. Credit checks that come from businesses sending you promotional offers and from lenders with whom you already have accounts are also soft inquiries.

Your score may tick lower, especially if the balance is near the card's limit, says John Ulzheimer, president of consumer education at SmartCredit.com. That's because your credit-utilization ratio is calculated for balances on individual cards as well as overall. And the longer the debt sits, the heavier the impact on your score. In addition, store cards tend to charge steep rates that may be retroactive to the day accounts are opened. So if you don't pay the balance before the interest-free period is over, you will rack up big charges.

Your income has no effect on your FICO score -- nor does your employment status. Your score would be damaged if you start to make late payments because money is tight. New lenders, of course, will consider employment and income when deciding whether to extend credit to you.

Yes, home-equity lines of credit are considered revolving debt -- you can continuously borrow money and pay it off up to a specified limit. But the FICO score categorizes home-equity lines of credit separately from credit cards, which are also considered revolving debt. So even if a reduced HELOC limit results in a higher ratio of debt, your credit score will not be affected, says Ulzheimer.

Getting rid of unused accounts -- and removing the potential to spend more money -- seems like a smart money move. And it could be worthwhile if you're tempted to overspend because of the extra cards or if the card issuer imposes an annual fee. But consider once again your credit-utilization ratio.

Say that each of the three cards you closed had a limit of $10,000, that you have three remaining cards with limits of $5,000 each, and that you have $7,500 in debt on the remaining cards. By eliminating the three cards with $10,000 limits -- for a reduction of $30,000 in your total credit-card limits -- you slash your overall limit from $45,000 to $15,000. And your credit-utilization ratio for all accounts jumps from a desirable 17% to a problematic 50%. In that case, you’d be better off keeping the accounts open and leaving the balances at zero.