Please keep in mind that Europeans have different customs.  You will go a long way toward being treated well if you know, and observe local customs.  How do you find out about these things?  The Internet contains a wealth of information about the customs of other countries.  Here is a good starting point.

European Etiquette

I can tell you a few things.  "Personal Zones" vary by country.  Italians are more likely to stand close when talking, and maybe slap your back.  That behavior is frowned on elsewhere, especially in Eastern Europe.  And, it is best that you NOT ask for a glass of water with your meal, unless you are at a "tourist trap" restaurant, where they have resigned themselves to this American oddity.  Also, wearing shorts in public is often not appreciated, except at the beach.  Germans expect firm handshakes.  The list goes on.  Find out as much as you can, in advance, about the places you plan to visit.  Use the Web!  A good search engine (my personal favorite is Google) will uncover a wealth of information.