This article concentrates on dining invitations to the home, as restaurant table manners tend to be quite cross-cultural, but the correct handling of cutlery applies to both venues.
When invited to lunch or dinner in Germany, be on time. Germans are punctual. If your hosts are a couple or a single lady, bring flowers. Avoid white lilies, white carnations or chrysanthemums as they are traditionally funeral flowers. A bottle is in order for a man; just never turn up empty-handed. Germans are house-proud. If you visit for the first time, admire a piece of furniture, a painting, a lamp or just the view. You will win hearts.
Do not sit down at the table before the host or hostess has shown you your seat and sat down themselves. When the first course is served, your host will usually say: Guten Appetit, which literally translates into: good appetite, meaning enjoy your meal. It's the sign for you that you may start eating.
If the first course is soup, it comes either in a plate in which case you use your spoon, or in a cup with two handles in which case you may drink it. If in doubt, watch your host. Never tilt your plate to scoop out the rest, and the soup is consumed without making a noise!
The fork is used in your left hand and the knife in your right and both stay there. Meat is cut as you go along and lifted to your mouth with the fork in your left hand. Potatoes, dumplings and meat loaf are never cut with a knife. If you pause, cross your cutlery on top of your plate, then continue. If the main course is asparagus, which is often the case in May and June when the vegetable is in season, you are supposed to eat it with your fingers and not to cut it. The metal of the cutlery is thought to affect the delicate flavor. You will find a crystal finger bowl, filled with water and a slice of lemon, by your plate. When you finish your meal, deposit your cutlery parallel and diagonally across your plate.
If you are given a linen napkin, slightly crumple it and put it next to your plate on the left when the meal is finished. Don't fold it up again. It indicates that you think your hostess doesn't own enough clean napkins and wants to use this one again.
Smoking after the meal is of course a very individual matter, but two rules apply: never smoke whilst someone is still eating and never between courses.
Don't lean across someone else's plate and don't put your elbows on the table, Don't ask for a second helping, but if you are offered one, you may accept a small portion. Don't forget to say Dankeschön (thank you) and to praise the food after the meal.
It will be rather rare to receive a home invitation for lunch or dinner in Turkey. However, if you have the good fortune to be invited, accept. Like in Germany, bring flowers, but never bring a bottle. Turkey is, after all, a Muslim country and you can make a big mistake there. You may bring chocolates instead.
When arriving, take off your shoes, even if your host tells you that it's not necessary. They have an array of slippers waiting by the door.
Food in Turkey, particularly chicken, is more often eaten with your fingers than with cutlery. Lemon cologne will be splashed over your hands before the meal starts and again afterward.
For religious reasons, lift only your right hand to your mouth. Your hostess will say: Afiyet Olson, which means: enjoy your meal and you reply the same. Make sure that the most senior diner is served before you and, although Turkish meals are a lively affair, never speak with food in your mouth.
Unlike Germany, asking for a second helping is a compliment, so go ahead. When using cutlery, the continental way applies, that is to say, fork in your left hand and knife in your right. Compliment the food and, if offered, accept a Turkish coffee to round off the meal.