Go to the « mairie » town hall of the city where people will stay. You must do it (as you must organize it from France, it's you, the person already living in France who is responsible for this).
If you live in Paris, Lyon or Marseille, as they are big cities, you'll have to go to the « mairie d'arrondissement », the district town hall.
If a familly will stay with you, one attestation will be enough but it must show the identity of all the members of the familly.
When you go to your "mairie", you will be given a form. Don't forget to bring the passport numbers of your guests, it's compulsory to fill this form in.
Back to the "attestation d'accueil" article