Civil registration of births, deaths, and marriages in France began in 1792. Because these records cover the entire population, are easily accessible and indexed, and include people of all denominations, they are a vital resource for French genealogy research. The information presented varies by locality and time period, but often includes the individual's date and place of birth and the names of the parents and/or spouse.
One additional bonus of French civil records, is that birth records often include what is known as "margin entries," which can lead to additional records. From 1897, these margin entries will often include marriage information (date and location). Divorces are generally noted from 1939, deaths from 1945, and legal separations from 1958.
The best part of French civil registration records in my opinion, however, is that so many of them are now available online. Records of civil registration are typically held in registries in local mairie (town hall), with copies deposited each year with the local magistrate's court. Records over 100 years old are placed in the Archives Départementales (series E) and are available for public consultation. It is possible to obtain access to the more recent records, but they are not usually not available online due to privacy restrictions, and you will generally be required to prove, through the use of birth certificates, your direct descent from the person in question. Many Departmental Archives have placed portions of their holdings online, often beginning with the actes d'etat civils. Unfortunately, online access to the indexes and digital images has been restricted to 120 years by the Commission nationale de l'informatique et des libertés (CNIL).
So how to find and access them?
Locate the Town/Commune
The important first step is to identify and approximate date of a birth, marriage, or death, and the city or town in France in which it occurred. Generally knowing just the department or region of France is not enough, although there are some cases such as the Tables d'arrondissement de Versailles which indexes the actes d'état civil across 114 communes (1843-1892) in the Yvelines department. Most civil registration records, however, are accessible only by knowing the town -- unless, that is, you have the patience to wade page by page through the records of dozens if not hundreds of different communes.
Identify the Department
Once you have identified the town, the next step is to identify the department that now holds those records by locating the town (commune) on a map, or using an Internet search such as "lutzelhouse department france." In large cities, such as Nice or Paris, there may be many civil registration districts, so unless you can identify the approximate location within the city where they lived, you may have no choice but to browse through the records of multiple registration districts. With this information, next locate the online holdings of the Archives Départementales for your ancestor's commune, by either consulting an online directory such as French Genealogy Records Online, or use your favorite search engine, such as "bas rhin archives etat civil."
Tables Annuelles and Tables Décennales
If the civil registers are available online through the departmental archives, there will generally be a function to search or browse to the correct commune. If the year of the event is known, then you can then browse directly to the register for that year, and then turn to the end of the register for the tables annuelles, an alphabetical listing of names and dates, organized by event type--birth (naissance), marriage (mariage), and death (décès), along with the entry number (not page number). If you are not sure of the exact year of the event, then look for a link to the Tables Décennales, often referred to as the TD. These ten-year indexes list all names in each event category alphabetically, or grouped by the first letter of the last name, and then chronologically by the date of the event. With the information from the tables décennales you can then access the register for that particular year and browse directly to the portion of the register for the event in question, and then chronologically to the date of the event.