1. Demand to see the actual proprietary score used before you agree to a loan or an insurance policy. You have the most leverage to get the truth before the deal is sealed.

2. We see no point in buying any consumer credit scores, given that they’re not the same ones used by lenders. But if you do, and a lender or insurer later tells you your real score is lower or higher, do what you’d do with any product that doesn’t deliver: Demand a refund.

3. Always shop for credit at multiple lending sources to find the best rate. Even if lenders won’t divulge their secret scores, getting rate quotes from several will reveal the best deal based on the numerous—and probably different—scoring systems used by prospective creditors.

4. Be sure to get your free annual credit report from each of the big three credit bureaus so you can look for and dispute errors. (Go to AnnualCreditReport.com.) We recommend that you stagger your requests and get one report from a different bureau every four months.