a preliminary hearing is oftentimes literally "before" the hearing. The preliminary hearing is oftentimes used to set up the parameters of the issues that the case is about so both sides can get ready for the hearing. Decide on witnesses, dates that need to be met, or make sure you're ready for the hearing. Maybe you'd need to get a document or provide a witness. Not sure what the judge will allow in your area. Also, kind of depends on the circumstances of the case. I'd be prepared for anything.
