Top tip: preferably don't cross a red pedestrian light, especially if you are not in the city centre of a big city and especially especially when there is a kid among the other people waiting
might seem silly, I know haha
If you meet up with somebody, I generally advise to be at least somewhat punctual. There is of course always be that person whos gonna be late, try to not be them
Don't be the ******* on the Autobahn who thinks that because there is no speed limit, they actually have to drive 240 km/h.
Public transportation depends on the city you are in and how centrally you live
generally, it is quite good (even though everyone always complains about the Deutsche Bahn). But if you live somewhat centrally and In a city like Berlin, you should probably be fine