If you have a warrant the last thing you should do is nothing. Having an outstanding warrant means you can be arrested at any moment, even for the smallest of infractions. You want to take of a warrant as soon as possible. In most cases, clearing up a warrant can be as easy as making an appointment to appear in court.
Contact the court that issued the warrant. Your original citation will have the court's contact information on the back. If you don't have the original citation, most courts make their contact information available online. Call the court and let the court clerk know that you want to arrange a court date to clear up a warrant. The clerk will be able to give you a date to appear in court.
Talk to your lawyer. You can hire a lawyer to represent you in court. Your lawyer will contact the courts and arrange a court date. Your lawyer will need your original citation if you don't have the original information give your lawyer the details of the incident, such as what the citation was for, the date of the incident and its circumstances.
Pay your bail. In some cases clearing a warrant can just mean paying a fine. When you contact the court, ask if there are any fines associated with your citation. If there are, ask if it is possible for you to pay the fine and clear the warrant without going to court.
Go to court. At your court date the judge will go over your citation and let you know what you need to do to clear the warrant. Depending on the citation, this could be anything from community service to jail time. In some cases you may just need to show proof that you satisfied the original citation.