Esskultur is important in Germany; Esskultur is the culture of food, dining, and manners. For most Germans, Esskultur begins when they are in high chairs and their parents teach them to eat when the adults are eating, to wait until the adults are finished to be excused from the table, how to use a napkin, and how to use their eating utensils.
In the US, manners vary widely and the manners you learn depends largely on what your family has taught you. We don't have one set of manners, and you can tell by the variety of food we eat; barbecue is largely eaten with the hands, pasta with a fork or perhaps a fork twirling the pasta with the help of a spoon. When alcohol enters the picture, it's a whole other ball game.
So here are some rules to live by to help you understand how Germans dine and to help you avoid some pitfalls along the way. For these rules, we'll assume that you have been invited to a friend's house or out to a business dinner.
1. Plan to Stay.
This American idea of party-hopping or "just staying for a little while" is incredibly tacky and rude. Germans do not do this. Either you accept the invitation and plan to stay for the evening, as delightful or as painful as it might be, or you politely decline.
2. Greet everyone with a handshake.
Yes, EVERYONE. Go around the room, shake hands, introduce yourself by your last name if it's a formal situation, by first name if it's informal, or somewhere in between for a mixed situation. People will fire their names at you and expect you to remember them.
Here's another great point: in the US, if you feel uncomfortable about trying to remember several names right off the bat, we make the joke "if there will be a pop quiz later," and everyone understands that they should remind you of their names when you speak again. This is a wonderful part of American culture in which we help each other out with remembering names. This is not so in Germany; they do not understand this joke. So keep that joke for this side of the ocean and if you need to, politely ask someone their name again as soon as you realize that you didn't learn it the first time.