First impressions create lasting impressions. This is true where table manners are concerned.
How one uses the napkins is also a display of one's dining etiquette. In a restaurant or in a hotel's dining room, place the napkin on your lap after everyone is seated. The napkin must be unfolded and not shaken. A large napkin can be folded in half and placed on the lap. In certain dining rooms, waiters may unfold and place the napkin on your lap.
At a private dinner party, unfold your napkin when your host/hostess does so.
If you are excusing yourself from the table mid-meal, loosely fold your napkin and place it next to your plate It is not considered good table manners to place your napkin on your chair. After the meal is over, place your napkin, semi folded, at the left of your plate.
Source: News Strait Times