Don't pay anything up-front
Watch out for "re-inventors"
Some companies will tell you that you can wipe your credit slate clean by "re-inventing" yourself with a new social security number. But that's not true! In most cases, what they plan to do is get you a new credit report by applying for an Employee Identification Number (EIN)--used by businesses--which resembles a social security number, and you're told to use it as such. But this practice, known as "file segregation," is a scam, and it's also illegal! Avoid any Credit Repair Company that suggests this practice.
Look for one that helps you help yourself
A good Credit Repair Company will tell you (for free!) what you can do yourself, such as writing letters to creditors and contacting the credit reporting bureaus about errors. Avoid any Credit Repair Company that encourages you to do anything illegal or unethical--such as disputing a legitimate charge or fee on your credit report.
Before signing up with any Credit Repair Company, make sure you check with the Better Business Bureau. They'll have records of any formal complaints against the company, so you can avoid scammers and rip-off artists.