Appeal deadline questions after an unemployment denial - what worked for you?

My claim was denied after 17 weeks of waiting, and the letter says I have a short window to appeal. This is my first time dealing with any of this. 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.