Because your credit rating is based on your actual history of borrowing and repaying money, there's no way to instantly boost it. Nevertheless, several simple measures will help you strengthen your credit over time:

Make all of your payments on time. If at all possible, never let an account become more than one payment past due.

Learn what's on your credit report.

Continue to check your credit report regularly, and correct inaccuracies as soon as possible.

To minimize the number of inquiries on your credit report, don't apply for multiple credit cards over a short period of time, or for a card you're not likely to get.

In general, try to keep your total account balance below 75 percent of your total available credit. For instance, if your cards have a total credit limit of $2,000, keep your total balance under $1,500.

Close accounts you don't need. To a lender, a high total credit limit signals potential overextension. At the same time, lenders want to see that you can maintain more than one account at a time. A total of three or four cards -- which may include gasoline or department store cards -- is usually good.

If your credit is severely damaged or you have a very short credit history, apply for a gasoline credit card, a department store card, or a secured credit card. Use the cards, and pay the balances in a timely matter

Are credit repair companies worth the money? 

Many advertisements on television, in newspapers, and on the Internet promise to correct a bad credit file for a fee. Such companies promise to erase negative information -- even a bankruptcy -- from your credit report. But in fact, negative information may be legally removed from your credit report only if it is inaccurate or if the 7- to 10-year reporting period has expired. In most cases, consumers willing to spend the necessary time and effort can do everything credit repair companies can do, for much less money. 

If you've already enlisted the services of a credit repair company, you're protected under the Credit Repair Organizations Act. Among other provisions, the CROA requires credit repair companies not to charge you until they've delivered the promised services. You have the right to sue any company that violates the act.