I studied in Berlin for 3 weeks and spent a weekend in Munich. A few things that I noted about my dining experience:
I usually sat myself. As an American this seemed strange as we have hostesses etc.
I was charged for water. But I have learned that Germany does not drink tap water as it is thought to not necessarily be as clean.
I was also informed that Germans do not tip. However they will round up to the nearest Euro denomination. There was a good question here about the evolution of tipping but I cannot for the life of me use the reddit search function.
It was totally fine to just have strangers sit with you at a table.
If anyone can share some insight on this to satisfy my curiosity that would be great!
Not an answer, but a clarification and a follow-up question.
German tap water is fine. People drink it all the time. Germany does have long tradition of bottled water, though (which goes back much further than the Perrier-inspired mineral water fetish that started in the 80s).
Germans do tip, but "properly". That is to say, you tip for good service, not as a matter of course.
Follow up question: What I'd like to know is why so many Germans eat pizza (and even burgers) with a knife and fork.