1. Do not drink and drive. Not even a tiny little bit. We don’t find this funny. We stick people in jail for a first offence — even if you didn’t get as far as leaving the parking-lot. People in bars might physically fight you / wrestle keys from you to prevent you from driving drunk.
2. Do not wear shoes inside private homes. There’s exceptions from this, but as a general rule, don’t.
3. People are pretty relaxed about nudity, and both men and women will for example change on public beaches without any attempt at covering themselves up. You are however expected to look away. No one will care if you glance, but please don’t STARE.
4. Do not unwrap flowers prior to giving them as a gift. (Germans do this.)
5. Don’t ask people what church they attend. Most attend none, and asking this is seen as intrusive, rude and downright weird.
6. Don’t assume that “socialist” is a synonym for “evil”.
7. Don’t be insulted if people don’t seem to “respect you” for being somehow distinguished. People are very informal here and being on a first name basis with anyone short of the King is the norm. Even the prime minister of Norway is most often referred to by first name; “Erna” (and previously: “Jens”).