Lenders long have used credit scores to determine whether to lend you money and how much interest to charge you. But these days, auto insurers, utility companies, landlords and even employers also are using your credit worthiness to determine your worth.

Credit scores are based on credit reports, which list your credit and borrowing activities. Under the Fair and Accurate Credit Transactions Act of 2003, all consumers will be entitled to free annual credit reports from the three major credit bureaus: Equifax, Experian and TransUnion. The law already covers consumers in the West, Midwest and South, and goes into effect elsewhere Sept. 1.

To get your no-cost reports, we suggest you bypass the many private Web sites proffering them – such as Experian’s FreeCreditReport.com, which automatically enrolls you in a $144-a-year credit-monitoring service when you sign up for a “free” report – and go instead to the government-mandated, credit-bureau-run site at www.annualcreditreport.com. But be prepared for difficulties.

In a study at the University of Utah, fewer than half of the people who had tried to get all three of the free credit reports from the site were successful. Vague instructions and overly difficult questions tripped up many.

When we tried the site, we had similar results, and encountered come-ons from two of the bureaus. In one, TransUnion tried to sell us a supposedly no-cost report for $9.50, with no obvious way to order a free one. In the other, Equifax offered us a credit score for $6.95.

(None of the three bureaus provides credit scores – known as FICO scores – with its reports. Equifax will sell you a FICO score for its report only; Experian and TransUnion offer proprietary scores that are not widely used by lenders.)

The Federal Trade Commission says that it is monitoring the free site closely, and that the credit bureaus are allowed to sell products on the site as long as it doesn’t interfere with consumers’ getting a free report. An easier way to get your reports and FICO scores, meanwhile, is through www.myfico.com, but the package costs $44.85.

However you come by them, you should review your FICO scores and credit reports once a year – or several months before applying for a loan – to check for errors, negative data, or any suspicious activity that may signal identity theft. (To learn how to decipher your credit reports, go to our home page, www.ConsumerReports.org, and click on Personal Finance. Then select “Your credit reports.”)

To clear up credit-report mistakes, you can contact credit bureaus online or in writing. Experts suggest using regular mail to file claims that may be more complicated to fix, such as one involving mistaken identity, so that you can include supporting paperwork. The bureau has 30 days to investigate your complaint and respond by either fixing the data or asserting that it is correct. Dispute errors directly with lenders if the credit bureau has decided that a complaint is without merit.

Once you’ve cleared up any errors, take steps to improve your credit score. (The FICO score can range from 300 to 850, though if yours is above 720 “you’re golden,” says Pat Curry, contributing editor at Bankrate.com, which monitors lending activities.)

Avoid late bill payments by automating the process, and keep a lid on spending in the months before you apply for a loan. Also, limit credit card applications. That’s because each time you apply for credit, a lender’s inquiry to view your report is noted, which can reduce your score. But don’t be afraid to shop around for a mortgage. Multiple lender inquiries made in a short period for the same type of loan count as one.