Many counties have websites for their court systems. I've seen some Magistrate Court websites that have good and pretty detailed instructions about how to proceed with taking an arrest warrant on a fellow citizen.
A few quick tips:
1-- Remember that although hearsay evidence is allowed to establish probable cause, the weight of the evidence may be diminished if you repeat what another key witness told you. Might be better to bring the witness to tell the judge himself or herself.
2-- Bring copies of whatever documents and paperwork you have. If you had a verbal agreement not a written one, bring your notes or make some notes about what was said, and when, and what happened next. Do that before you go to court. It will make telling your side of the story go smoother and faster, which will please the judge.
3-- Everything you say should be relevant toward satisfying the criminal code section you're charging the other guy with violating. Try not to vent about any other bad things this person did to you or to anybody else, unless it's very similar to what you're accusing him of doing now. A pre-warrant hearing isn't about people's character. It's about finding probable cause, or a lack of P.C., that a certain person committed a certain act or series of actions, in a certain county, on a date (or range of dates) that shows the Statute of Limitations has not expired.
4-- If you want a felony warrant instead of a misdemeanor one, make sure to mention the value of what was wrongly taken / converted. State to the Court how you know approximately what it's worth today (which may be considerably different from what it was worth brand-new).
None of this is legal advice, of course. Just some tips for anybody going into magistrate court or even small claims court on a civil matter.
Good luck.