When being invited to lunch or dinner at a friend's house or even at a restaurant, you have to keep your table manners at their best.
Here are a few tips that will have everybody impressed:

Gifts: When you are invited to someone's house for lunch or dinner, bring along a token of your appreciation. It can be as simple as flowers or chocolate.

Clothing: When you receive an invitation, ask for the dress code! It isn’t necessary if the invitation is for an outdoor barbeque for example. Consider the purpose and type of the invitation and the time as well for choosing the appropriate outfit.

Napkin: Always place the napkin in your lap when you first sit down at the table. Fold it so that a quarter of it is folded over the top.

Posture: Relax and enjoy your time with others. Do not rock the chair or slouch your back, and don't put your elbows on the edge of the table.