Denied unemployment, how do I appeal? - what worked for you?

My claim was denied after 18 weeks of waiting, and the letter says I have a short window to appeal. Any experience at all would help. 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?

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