Collect all evidence and correspondence with said credit bureau before seeking legal advice or filing a lawsuit. Keep in mind that credit bureaus have seemingly limitless resources, and you'll need airtight evidence confirming malfeasance or injustice to have shot at winning. Send demand letters to the credit bureau several months prior to filing suit. Keep copies of these letters and any return correspondence.
Contact an attorney with legal expertise with credit and debt law (see Resources). Prior to signing a retainer, ensure your attorney has experience with credit bureau prosecution or credit card delinquency (i.e bankruptcy law). Advise your attorney of your claim--false reporting, identity theft, demographic inaccuracies--and provide him/her with the documents you've collected to support your claims.
Familiarize yourself with The Fair Credit Reporting Act. It allows very little latitude when suing a credit bureau. The simplest and most effective way is to file a defamation suit (that is, injuring your character or standing in public). This works because, essentially, a credit bureau reporting inaccurate information is misrepresenting you. Speak with your attorney further on this subject.
Develop a strategy with your attorney, and go to the courthouse to officially open a lawsuit against the offending company. This can usually be handled in a day. Your attorney will handle the delivering of the summons to the respective agent of the company. (This is normally referred to as "being served.")
Once filed, send a certified letter to the credit bureau informing them of the lawsuit, the pertinent court details, your complaints and the action that will be taken. Retain a copy of this letter and any following correspondence.