Got a denial letter for unemployment, what now? (update)

I got a denial letter last week saying I left my job voluntarily, but I was let go as a teaching assistant. I worked as a teaching assistant before this. My employer's version of events does not match mine, and I have emails that show it. If you have appealed before, what helped you prepare?

I printed my emails in order and wrote a one-page timeline. The hearing officer kept going back to it.

Keep everything in writing and save the confirmation numbers. It saved me later.