Although savoir vivre is uniform throughout the world curious customs make it almost impossible to be polite in each separate society. One could understand to have both hands above the table as French oblige to do or to be around the table for at least everyone has finished their meal as Spannish suggest.
But what about use your fingers when asparagus is on site as English propose or do not cheer if you drink a beer as Hungarians do not? These weird customs were defined long ago and in a sense have defined the cultures of these countries; they have defined their heritage. So, although you know your customs you should be cautious when you are in other countries! Enjoy.