Denied unemployment, how do I appeal? - 21 weeks in

My claim was denied after 21 weeks of waiting, and the letter says I have a short window to appeal. I have been trying to stay organised about it. The letter lists a deadline and a hearing process, but it is hard to follow. 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.