Okay here are some random things I have learned, but may or may not be valid anymore, or in all households:

Do not take a bath ever in the home of someone you are staying with and do not know very well...

The notion popular or common in the US of 'my house is your house' is not as common in France, and you really must play and welcome the role of guest when invited into someones home. They are happy to serve you as their guest, and you must in turn graciously play your part, meaning make yourself comfortable, but not too comfortable...

When invited to someones house for apero or dinner, do not serve yourself a glass, or refill your glass, especially if you are a woman - wait until the host or someone else offers you more - or invites you to servez vous...although I have had debates on this. Supposedly when a lady is out and her glass remains empty, it looks bad for her to fill her own glass, but it looks worse of her date for not being attentive enough...but if anyone knows the real etiquette on this, please shine some light!