Hi, see this for official tips:
https://www.uscis.gov/forms/filing-guidance/tips-for-filing-forms-by-mail
TL;DR:
- Don't staple things
- Photos to be printed on regular paper with captions (when, where, who's on photo). Three photos per page is typically good.
Who's ownes or pays the lease for apartment?
Scans of DLs / state IDs showing matching address would help.