第一句：Ideal posture is to sit straight, but notstiff, against the back of the chair.
A: What is the proper way to sit at a dinner table?
B: Ideal posture is to sit straight, but not stiff, against the back of the chair.
B: Hands, when one is not actually eating, may be in the lap. Tipping one’s chair is unforgivable.
第二句：What is the proper way to handle a napkin at dinner?
A: What is the proper way to handle a napkin at dinner?
B: Ordinarily, as soon as you are seated, you put your napkin on your lap.
A: How about at a formal dinner?
B: At a formal dinner, you wait for your hostess to put hers on her lap first.
But I know nothing about a western dinner.
When the meal is finished, or if you leave the table during the meal, put the napkin on the leftside of your plate, or if the plates have been removed, in the center.