Got a denial letter for unemployment, what now? - what worked for you?

I got a denial letter last week saying I left my job voluntarily, but I was let go as an IT help-desk technician. I am in Chicago, in case local advice matters. I have not done a hearing before and I am nervous. 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.

File the appeal before the deadline, even if you are unsure. You can gather documents afterwards. That is the one part I would not wait on.