If you're a drinker like me, European beers in Europe will not give you as much of a hangover as American beers do in similar quantities. Not sure where you're going in der Vaterland, but keep an eye out for Berliner.
Stay away from Turks, Albanians, etc. unless it's to get yourself a döner kebab on the street.
Don't tip as they can find it offensive since servers already get paid a normal wage.
People also have no concept of personal space. It was nothing for people to bump the hell out of you at a bar.