Paris - Parties
When you are invited to dinner by a French family be sure to arrive no more than 10-15 minutes later than the invitation time, if it cannot be helped, call and inform your host that you are arriving late.
If you know you are participating to a large dinner party then you might consider pleasing the host by sending flower arrangement which can be used for the evening.
Dress code is never casual, but avoid being over-dressed, unless is specified in the invitation. If in doubt call on the host and ask what is the dress code for the evening.
When greeting the host and hostess, unless you are already in friendly terms with them stick to the handshake, respecting the order (women first then men) and making sure to say "bonsoir Madame/Monsieur" (good evening Madame/ Mister) followed by the last name. First name should be introduced only upon specific request by the people.
A card can be sent the following day to thank your hostes of the dinner/party, but even a phone call is these days considered polite and acceptable.