Start with place, time and jurisdiction
Start with the commune and department that held jurisdiction at the date of the event. Departmental archives usually publish the digitised registers, while FranceArchives helps locate national and local collections. Paris and former French territories can require specialised series, and commune boundaries or names may have changed.
Follow the strongest record sequence
Use civil birth, marriage and death registers from 1792 onward and parish baptisms, marriages and burials for earlier research. Ten-year tables can locate an act efficiently. Population censuses, military recruitment registers, notarial records and succession material can then expand a person beyond basic life events.
Preserve evidence and local context
Cite the department, commune, register type and date range, act or page number, image and archive. Marginal annotations may point to later marriages, divorces or deaths. Preserve the exact act text and distinguish the event date from the registration date before creating a preferred conclusion.