It will say what you have to submit (assuming you are doing it online, it's easier). Some examples include your last 3 years of tax, green card, birth certificate of your US spouse, birth cert of your children etc. You can submit extra documents as well. Pretty much everything you already submitted for adjustment of status + all the new stuff.
I submited 60 documents in total and the Immigration Officer at the citizenship interview thanked me for making this easy for her because she was able to approve me in a month and a half!
Good luck, N400 is easy but still a lot of paperwork!