That's a very difficult question to answer. The problem is that Europe is one huge place full of different cultures and they all have their own etiquette. So I recommend that you purchase a good travel guide and follow the local customs. Also at the moment I would recommend that you don't talk politics or recession while there. This may not be welcome. I also recommend that you read my hub "why slow food was invented in Europe and fast food in North America". It may give you a pretty good picture about the eating and socializing etiquette there.