Arrange automatic payments for every card or loan. Credit scores are extraordinarily sensitive to whether you pay your bills on time, so don't let travel, a busy schedule or a simple brain cramp trash your scores. Most lenders will let you set up automatic payments that take an amount you specify -- the minimum payment, a set dollar amount or the full balance -- every month from your checking account.

Don't let disputes go to collections. Yes, your insurance should have covered that bill; no, you shouldn't have to pay for a broadband connection that doesn't work. But if you let a commonplace problem like these escalate, your account will be turned over to collections and become a big black mark on your credit reports. Pay under protest and get your revenge in small claims court. (Don't get sued yourself, though: Lawsuits and judgments are also major stains on your credit reports.)

Give your limits a wide berth

Pay down and spread out your debt. More than a third of your FICO score depends on how much of your available credit you're using -- your so-called credit utilization. The FICO formula likes to see big gaps between your balances (whether you pay them off each month or not) and your limits, especially on credit cards. (You're rewarded for paying down installment debt, such as mortgages and auto loans, but your scores improve much more dramatically when you pay down revolving debt such as credit cards.) In short, it's better to have small balances on several cards than a big balance on one card.

A balance is a balance. You have to worry about your credit utilization ratio even if you pay your balances in full each month. The balance that's reported to the credit bureaus is typically the one on your last statement, not the balance that's left over after you pay your bill. So if you charge $9,000 on a $10,000 card, it's going to look like you're using 90% of your limit (which is really, really bad), even though you paid off the balance in full when you got the bill.

Shoot for 10%. The less of your available credit you use, the more FICO rewards you. Keeping your credit utilization below 30% on your cards is good; getting it below 10% is even better. If you regularly use more, ask for a higher limit, spread out your charges on more than one card or make two payments every month -- one just before your monthly statement closing date to lower the balance reported to the credit bureaus and a second one just before the due date to avoid late fees.

But don't let your cards gather dust. Overloading your cards is a bad thing for your scores, but so is not using them at all. The scoring formula prefers to see accounts that are being actively used rather than sitting on a shelf. Even a little activity is better than no activity.

Push back against lower limits. Credit card issuers are reducing limits right and left. In fact, one banking analyst estimated that by the end of 2010, risk-averse companies will have slashed in half the $5 trillion in credit limits that existed before the financial crisis. This can be awful news for your credit scores, but you can, and should, try to push back. If you can't get the issuer to reverse its decision, try to move your balance elsewhere.

3 ways to erase credit card debt

Move debt to installment loans. If you've got high balances that you can't pay down quickly, consider transferring the debt to a personal installment loan. The interest rate you'll pay is typically higher -- 13% or so for people with good credit, up to 22% for those with fair credit -- but the scoring formula treats installment loan balances more kindly than the same debt on credit cards.

Move debt off your credit reports entirely. You can make debt seem to disappear by paying it off with a loan from a friend, family member or retirement plan, none of which typically show up on your credit reports. If you're tempted to tap your retirement account, though, let me be clear: I am not a fan of 401k loans. Lose your job, and any unpaid balance can quickly become a tax nightmare. It's an especially bad idea if your finances are on the edge, because credit card debt can be erased in bankruptcy; 401k loans can't.

Play the home equity card cautiously. Moving a credit card balance to a home equity loan or line of credit may improve your scores but put you at greater overall financial risk. If you fail to pay the bill, you could lose your home. Also, as with a 401k loan, you're turning unsecured debt that could be wiped out through bankruptcy into secured debt that typically can't.

Walk a fine line on plastic

Don't close accounts or let them be closed. Closing accounts can't help your scores and might hurt them. Yet many issuers these days are slamming shut inactive cards rather than continue to carry these unprofitable accounts. If you've got cards you haven't used in a while, take them out for dinner or a movie, and pay the balance promptly. Better yet, use them to charge a regular expense, such as your electric bill, and arrange for automatic payments.

Apply for credit sparingly. Applications for credit don't ding your scores as much as some people fear; typically, you lose five points or less. But when every point counts, such as when you're in the market for a mortgage or a car loan, you don't want to squander any of your scores. Wait to apply for any other credit until you've secured the loan you want.

The lower your scores, the longer it will take to crawl your way back up the FICO scale. But progress is possible, and anyone can hit the 740 mark in time by using credit consistently and responsibly.

Liz Weston is the Web's most-read personal-finance writer. She is the author of several books, most recently "The 10 Commandments of Money: Survive and Thrive in the New Economy" (find it on Bing). Weston's award-winning columns appear every Monday and Thursday, exclusively on MSN Money. Join the conversation and send in your financial questions on Liz Weston's Facebook fan page.