Names and Titles
Use last names and appropriate titles until specifically invited by your French host or colleagues to use their first names. First names are used only for close friends and family.
Colleagues on the same level generally use first names in private but always last names in public.
Address people as Monsieur, Madame or Mademoiselle without adding the surname.
Madame is used for all adult women, married or single, over 18 years of age (except for waitresses, which are addressed as Mademoiselle.)
Academic titles and degrees are very important. You are expected to know them and use them properly.