When you are invited somewhere for a meal, wait for the hostess (or host if there isn’t an hostess) to begin eating. Follow her lead for praying, toasting, beginning and ending the meal, etc. In REALLY polite situations, she will even nod to let you know who to talk to. If it is a “banquet” where there are more than one table of guests, it is appropriate to wait for your entire table to be seated and served.