Shutting the light when you leave the room. “Don’t waste electricity!”
I had five year old friends of my kids call me by my first name and I was put off. Their mother encouraged them to do it. When I said I was raised to say Mr. or Mrs. their mother said where she’s from she grew up calling the adults by their first names. She didn’t correct her kids to respect me by saying Mrs. instead. I let it go but felt annoyed and that they were snotty kids. Other kids would say Miss and my first name. It’s the southern way. This felt more respectful and also warmer than the formal way I was raised.
Other rules that come to mind are observing superstitions. We had many. I broke a mirror and did have 7 years bad luck.