Got a denial letter for unemployment, what now?

I got a denial letter last week saying I left my job voluntarily, but I was let go as an event coordinator. I worked as an event coordinator before this. The letter lists a deadline and a hearing process, but it is hard to follow. If you have appealed before, what helped you prepare?

Thanks for writing this out. I went through something close to it 14 months ago, and it settled down once I kept a simple log of every call and form.