The situation is different for companies and individuals.
Companies: For companies, get a D&B Business Information Report and/or an Experian report. D&B Reports are often the best information available, but they can be expensive. They are available through the D&B Small Business Credit Solutions site and other vendors (see "Dun & Bradstreet Reports"). Experian (formerly TRW) Reports are available for cheap through SmartBusinessReports.com and other vendors (see "Experian"). Skyminder sells credit reports from a wide range of vendors covering just about all countries.
Individuals: The public is generally prohibited from getting credit reports on individuals by the Fair Credit Reporting Act (15 USC 1681 et. seq.; the complete amended act is posted by the Legal Information Institute). There are several exceptions, found at USC Section 1681b (Section 604 of the Act). Law librarians who are asked to get credit reports may want to copy this section and show it to the requesting attorney to see if any of the exceptions apply. For more information, see "Fair Credit Reporting Act."
If an exception does apply, some firms already have a system for obtaining credit reports (e.g., for pre-employment screening or check the solvency of potential clients). If so, that is probably your easiest and cheapest way to get the reports. Alternatively, you can place an order with a company that retrieves reports. I have been told that the credit bureaus no longer permit vendors to sell reports directly to law firms (other than collection firms). However, CheckMate will draft a summary of the report including the substantive information, once they receive a written explanation of your permissible use. Alternatively some companies that will not work through a law firm, such as Accurate Information Services, will still sell reports directly to businesses with a permissible purpose; you can refer your client to work with them directly. [If you find a company that will sell personal credit reports to law firms, please let me know].
In theory, you can get also credit reports directly from the three big credit bureaus: Equifax (800-685-1111), Trans Union (800-916-8800) and Experian (888-397-3742). This will work fine if you are requesting your own credit report. If you are asking for a report on someone else, it is almost impossible to work with the credit bureaus directly (unless you are a bank, landlord, etc.), and you are better off paying an intermediary, if you can find one.
Finally, you may be able to get some information about a person's credit situation by searching public records for indications of assets and liabilities - such as liens, bankruptcies, home ownerships, etc. - from TLO, KnowX.com, Accurint, Lexis or another public records database vendor.
Another alternative: Some Web sites and private investigators will get you credit reports on individuals. I don't know how they do it, and I don't know if it's legal, but the practice is not uncommon.
If you want to get a copy of your own credit report, you should be able to get it free on AnnualCreditReport.com or by calling 877-322-8228. If it isn't, contact Equifax (800-685-1111), Experian (866-200-6020) and/or Transunion (800-916-8800) directly, or use one of the services discussed above. For more information, check each company's Web site.
Credit Scores: A credit score is a number that represents the creditworthiness of a company or individual. The numbers are calculated by private companies. Fair Isaac Corporation produces the well known FICO score. They do a special version called FACTA, BEACON for Experian.