Gather identity and family information, a clear statement of the specific proposal under consideration, and questions about eligibility, the source of funds, and the current official instructions, then follow the government's directions for any subsequent forms.
Rely on a dated, official source
The official website indicates that applicants receive further USCIS instructions after an initial step; review those current requirements rather than assuming a prior applicant's file can simply be reused. Keep a record of which version of the instructions the plan was based on.
Keep legible copies of the expired and replacement passports, the renewal explanation, prior submission receipts, and the exact identity data entered online. Identity and background records may be requested during vetting and visa processing, and the official FAQ expressly refers to a required medical examination. A family builds a chain from birth record to marriage certificate to passport, and one link — a first marriage that ended, an intermediate passport issued abroad and long since surrendered — is not in the box. After payment, wait for the official instructions before assembling documents, since the request defines what is needed and a speculative package usually has to be redone.