I see that my 2 cents today are worth about .013 Euro cents (which is to say, not worth much!). I agree with much of what she said but will make a few comments.
Regarding saying "
bon appetit": I've read that advice elsewhere (perhaps the same place Elaine Sciolino did, along with the advice to never use the powder room in somebody else's home). Now, she and I obviously do not run in the same social circles, and perhaps things are different among the people she frequents, but when I asked my French acquaintances about this, they all agreed that they had never heard such a thing and that it was customary and quite acceptable to say "bon appetit" when beginning to eat the meal.
As far as having to use the powder room, I say good grief! No reasonable person should expect you to be uncomfortable, especially if you've gone through an aperitif, wine and/or water with dinner, and possibly a digestif as well... though I do agree that I wouldn't ask for "les toilettes" but rather ask politely and discreetly if I could wash my hands, which gets the idea across in a more genteel fashion.
Note that the "
bise" (normally in this case one would say "
bise" rather than "
bisou", as in "
faire la bise") can be 2, 3, or 4, depending on the region of origin of the persons involved. Even the French in a particular region don't always agree on how many it should be, so follow the other person's lead and be prepared to be a good sport if there's an extraneous
bise or two.
If you've seen the prices of lingerie here (and I'm not even referring to the exchange rate for us Americans), it's easy to understand how French women can spend 20% of their clothing budget on lingerie. Lingerie is important here, even if you're just dressing for yourself. And if you're not, well, most Frenchmen are appreciative of nice lingerie too.