I've found the best way to get polite service in Europe is try to fit in.  Otherwise dress like they do (no track suits, tennis shoes or other clothes that make you look American), don't always be asking where the nearest McDonald's is, try the local food instead.  Except if in the UK or Ireland where English is the main language or Scandinavian Countries or Netherlands where virtually everyone speaks English, make an effort to speak a few words of the local language and if you cannot always ask if the person speaks English before speaking unless on their name tag it shows they do.  While English is widely spoken as a second language in Europe, not everyone speaks it and unlike the US most Europeans take pride in knowing multiple languages so even if they speak English at least making an effort is appreciated which I find Brits often do but not Canadians and Americans.