If you are trying to rebuild your credit score, an excellent resource is the website www.myfico.com. According to the site, myFICO(R) is the consumer division of FICO. They are the company that developed the global standard for measuring credit risk with credit scores.
Anyway, there is a lot of valuable information on the site. You can buy your credit score, you can see what is hurting and what is helping your score, and you can participate in their forums and learn a heck of a lot about credit, and how to rebuild it if your score is "less than perfect."
There is an example of a credit dispute letter that you can use to dispute erroneous entries on your report, along with detailed instructions about how to dispute an error. There are also simple explanations about the credit laws that protect consumers, including the Equal Credit Opportunity Act (ECOA), the Fair Credit Reporting Act (FCRA), the Fair Credit Billing Act (FCBA) and the Fair Debt Collection Practices Act (FDCPA).
This website is an excellent resource and I highly recommend it if you are trying to improve your credit, or if you just want to check your credit scores and get advice on how to improve them.