1. First of all you need to Go online on Annual Credit Report's website. here you can request all major 3 credit scores for free guranteed. you dont need to pay a penny to get your all three credit reports.
2. To start the credit report processing, you need to select the state of your residence and next you will click on "Request Report". next you will be asked for quick information about your social security and addresses in history.
3. You need to complete the identity verification process by answering few questions about your credit history and your various residence history over few years. you might be asked to submit the proof of your identity through mail if credit report company's website wont able to identify your identity. you no need to worry if website doesnt verify your identity, it doesnt mean that something is wrong with your credit.
4. Once you get your credit reports from all three agencies, you need to check and compare the information you recieve against your own financial records and match them.
5. You should file the dispute with credit report agency where you get the report, if any errors you found in reports and list that error in your application of dispute. All credit report agencies maintain an online dispute submission forms on their websites and also keep you posted on progess of dispute or you can check online by yourself.