In the long run, the recognition that it’s at least as important for us to be in situations that are comfortable, and where we thrive, than it is for us to “fit in” with situations where we can’t be ourselves.
But in the short term, I would say “active listening”. If I could go back in time and teach my younger self one social skill, I would teach myself how to navigate a conversation mainly by keeping the other person talking. I can even tell you the precise textbook I’d use. Geldard and Geldard, “Basic Personal Counselling”, part 2, “Basic Principles and Skills”.
I won’t pretend I’m always great at it, but when I was around 30, I took a course for telephone crisis counsellors that was based on the Geldard and Geldard principles. It significantly upgraded my ability to engage with other people.
What I find most useful about active listening is that it is based around a set of “micro-skills” that can be learned, practiced, and successfully applied across a wide range of situations. But they are micro skills, not behaviors. It’s not about learning the “right” way to interact with other people, or being indoctrinated into uncomfortable behaviors. It’s a set of building blocks that can be added together to create positive interactions with other people.