Got a denial letter for unemployment, what now? - 19 weeks in

I got a denial letter last week saying I left my job voluntarily, but I was let go as an accounts payable clerk. It has been weighing on me all week. The letter lists a deadline and a hearing process, but it is hard to follow. If you have appealed before, what helped you prepare?

Keep everything in writing and save the confirmation numbers. It made the follow-up calls so much easier.