you should not give gift with a seal or mark of the company because it is considered inappropriate to express for nationals of France.
you should have a little gift for trustees to homeowner such as flowers wine. if the house with children might be candy or chocolate for kids
you should be told in advance before visiting it is impolite if you do not tell them in advance before going to visit
you should not stand up from the table until everyone is done eating.It is impolite if you get awayfrom the table