I have a different take: I try to not be an unpleasant person.
I suffer from a particularly nasty Voltron of ADD and Asperger’s. High-functioning, yes. But it’s still a non-trivial level of neurological fuckery. This means that my social actions and reactions are… different. Sometimes they deviate significantly from the socially accepted baseline. So to be “nice”? What is nice? How to categorize that, measure that, evaluate that? “Nice” could be different for each person I come across.
So to avoid driving myself crazy, I have flipped things and simply concentrated on not being an unpleasant person. To not be rude, not disrespectful, not frightening or combative or creepy. It ends up being a little easier to categorize, define, and measure in that regard, because it involves not doing something instead of doing something. It is avoiding a baseline instead of trying to meet it.