10 Ways To Improve Your Credit (Forbes.com)

1. Maintain a small number of revolving accounts with high limits, and pay off the balances each month.
2. Don't apply for credit indiscriminately. Lots of 'hard inquiries' in your credit file will damage your credit rating.
3. If you accidentally make a late mortgage or other loan payment, ask the lender for forgiveness "just this once", "It works."
4. Get a new credit card and don't use it. Your FICO score is based upon a ratio of the overall percentage of outstanding debt divided by available credit. A new credit card increases your total available credit.
5. If you have a credit card balance, make larger payments than the minimum and make payments on time--no matter what.
6. One of the most damaging aspects of credit card debt is owing more than the limit on the particular card. Pay this off first. Try negotiating interest rates with your credit card company.
7. Don't let companies do unnecessary inquiries on your account, says Elaine Scoggins, a certified financial planner in Seattle. For instance, if you are shopping for a car, but don't plan to buy yet; don't let the dealer check your credit. If you don't need it, leave it. Only seek credit when you need credit. Ten percent of your FICO score is based on new credit account opened.
8. If you are getting a divorce, be sure to contact creditors so you can replace joint credit cards and other loans with ones in your own name.
9. Never max out a credit card account. It is better spread the debt across several accounts. A good rule of thumb is not to be above 80% of the actual credit limit. It is better to owe $5,000 on two cards each with a $5,000 limit than it is to owe $5,000 on one card with a $5,000 limit.
10. Never close the lines of credit that you use responsibly. Keep them open and maintain them for a long time, and your score will improve. However, if your debt is reasonable, you might consider closing unused credit lines. Close the account and get confirmation in writing that they are closed.