Denied unemployment, how do I appeal? (Seattle)

I got a denial letter last week saying I left my job voluntarily, but I was let go as an IT help-desk technician. There are 8 people counting on me, so I am trying to be careful. 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?

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.

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