I'm going to focus on the 4 forms that I needed to include with my application that were required by the Los Angeles consulate. The consulate documents you may need to submit could be different than what I did, but from the other jurisdictions I have seen this far, they were the same. Be sure to keep these documents in mind during your journey and don't wait until near your appointment. The forms require lists of residences of yourself and all of your bloodline relatives to the best of your knowledge. Any living relatives need to sign the form and get it notarized. Here is some information on the forms I had to fill out:
Form 1
This form is the first page of the application. This is where it asks for all of your personal information and where they can contact you. This form also has a section of a quick run-down of the relatives in the line you are choosing to use. This form does not specifically say that it needs to be signed at the consulate or notarized ahead of time. I had mine notarized anyhow.
Form 2
This form is your list of all the cities and states that you had lived in with approximate dates since you were 18 years old. This one is also signed to certify that you have not renounced your Italian heritage. If you wonder if you have, then you probably haven't. Naturalization does this automatically, but you probably have a good understanding of how that works by now.
Form 3
This form is basically the same as Form 2, but this is for any living ancestor. For me, this was my father. I spent some time with him on the phone and we brainstormed all the places and years, then I mailed him the letter and he had signed it and had it notarized, then sent it back to me so it can go into by binder/application.
Form 4
This form is basically the same as Form 3, but for any deceased ancestor. During this process, I did learn with a lot of certainty all of the places that my ancestors had lived. They didn't travel much as they did not have much money it seems. This form also needs to be signed by you and notarized.