Start with anything that establishes precise dates: travel records, passport stamps, I-94 history, prior notices and decisions, and pay or enrolment records for the period in question. Bring the complete originals of prior applications rather than a summary of what was submitted.
Reconstruct the timeline before interpreting it
Build a dated timeline of entries, departures, filings, decisions and periods of work or study, and mark every point you cannot document. Counsel can then work with facts rather than impressions. Where a record is missing, ask what can be requested and how long that takes. Doing this first also prevents a later application from contradicting something already on file with a government agency.
The file holds passport details, credentials, salary information, and possibly family records, so it belongs in an encrypted store with a backup rather than in an inbox. Check prior application copies, correspondence with counsel, appointment records and relevant passport pages. A certificate hanging in an office establishes that the designation was granted; a current good-standing letter establishes that it still stands. Citizenship is proved by a passport or citizenship certificate, not by a residence document. Verify that names, dates, field of study, and awarding institution agree across every item.