You need a subpoena to get someone to testify in court. The court clerk issues it for the judge presiding over your case. Once you get the right information on the form, it's up to you or your lawyer to make sure the subpoena gets served to the right person on time. Follow the steps to make sure your subpoena is served legally.
Request the court clerk issue a blank subpoena. This is done when the witness doesn't want to testify or you need documents as evidence that you don't have access to on your own (someone else's bank statements, for instance).
Check the address where you think your witness is. Most subpoenas must be served to the witness personally, although there are certain exceptions. You may be able to serve someone else at the place you know the witness lives or works. Or you may be able to leave it if you've tried serving it a couple of times and no one was there.
Locate the witness you want to subpoena if she's not where you thought she was. This can be tricky if it's someone who's had problems with the law. Hire a private investigator with experience in skip tracing who has access to resources for finding people.
Fill out the subpoena form so the witness knows where and when the trial is and who's involved. It should also tell them what documents, if any, to bring and what the consequences are for not showing up in court.
Get the subpoena notarized.
Contact your local sheriff's office to have them serve the subpoena. You'll need to give them the original subpoena and a copy to give to the witness served.
Consider hiring a process server to ensure your subpoena gets served properly. Some states require process servers be licensed. Check Nationwide Process Servers Association website to find one in your state.
Your lawyer can also issue a subpoena because he's an officer of the court. Write a letter with the subpoena stating you don't need anyone to appear in court if you just want access to documents to make your case. You'll have fees to pay all along the way. Look into applying to the court for a waiver if you can't pay them.