Denied unemployment, how do I appeal?

I got a denial letter last week saying I left my job voluntarily, but I was let go as a production planner. I would rather hear the honest version than the polite one. The letter lists a deadline and a hearing process, but it is hard to follow. If you have appealed before, what helped you prepare?

Stay calm and stick to facts. Mine lasted about thirty minutes and felt more like a conversation than a trial.