The best way to find out if you have an FBI file is to file a Freedom of Information Act (FOIA) request with the Federal Bureau of Investigation. You can also use FOIA requests to obtain files from other American government agencies such as the Central Intelligence Agency (CIA). By law, these agencies must provide people with copies of their files when asked to do so, although portions of the file may be redacted for security reasons.
Depending on who you are, your FBI file may be quite entertaining or rather dull. As a general rule, anyone who is involved in activist activity has an FBI file, although it may be slim. FBI files are also kept on people who are suspected in involvement in illegal activities like human trafficking, the drug trade, financial fraud, and murder. Even if you are not involved in activism or illegal activity, the FBI may have a file on you because you are associated with someone who is; be aware that the FBI will probably not tell you which of your associates has caused them to open an FBI file on you, as this can compromise an investigation.
In addition to acquiring your own FBI file through an FOIA request, you can also request files on other people and organizations. In addition, you may want to take advantage of the FBI's FOIA library, which contains records on people and organizations of historical interest. In addition to simply being interesting, some these files can provide intriguing historical context and you may find yourself learning a few new things.
The FBI actually has a special form which can be used for FOIA requests, although you can also simply submit a notarized written request. You will need to state your name, along with any other aliases you use, and you should include your address and any other contact information such as a phone number. Other identifying information like a Social Security Number or dates of particular interest can also be included. You are also required to submit a notarized form which confirms that you are who you claim to be; if you want to obtain the FBI file of someone else, you must get him or her to fill out this form, authorizing the release of the FBI file to you. For deceased family members, include a copy of the death certificate.
Once the FBI receives an FOIA request, they will send back a letter acknowledging receipt and providing you with a tracking number. This number can be used to check up on the progress of your file; it can take weeks or months for the agency to collect and copy the information in your FBI file. Filing an FOIA request is free, but you may be charged a small fee for duplication of the relevant records; if this is the case, you can stipulate the maximum amount that you are willing to pay.