False allegations about you or your company can have devastating effects, both on your personal reputation and your bottom line, so it's important to deal with them straight away by filing a lawsuit. Generally, you will need to meet strict conditions in order to win a libel or defamation lawsuit. If you feel your case has merit, you can start the ball rolling on a lawsuit that could repair your reputation and perhaps even win you monetary damages.
Determine if your lawsuit can win. In order to win a defamation case, you will need to demonstrate that a person published or made statements about you that were intended to be factual and reflect negatively on your image. Generally, the allegation must be demonstrably false. Also, you will need to prove that the allegations in question were "of and concerning" you. If you can't prove these things, you have a slim chance of prevailing.
Gather evidence, as you are the one who must prove guilt. Collect statements by the defendant and any documentation proving that the statements were about you. Collect proof that the allegations were false; for example, if a newspaper suggested that you were arrested for drinking and driving, get a police report that indicates the charge was for speeding and that the police never mentioned alcohol. Find evidence that these allegations negatively impacted you; for example, you could include correspondence from former customers who wrote that they will never do business with you again because of the allegations. Finally, collect proof that the allegations were made to a third party.
Contact a lawyer who specialises in libel and defamation lawsuits. The lawyer can advise you on the merits of your case and what more you will need to bolster it.
File the lawsuit if you and the lawyer agree that you have a good case. The lawyer will be able to file it in the appropriate venue.