Anyone who has a dog knows how it works. When you observe behavior you want to encourage, you reward the dog; the dog is then more inclined to exhibit the behavior. You might be surprised to see how well it works on humans. My wife and I have used it on our kids, with noticeable behavioral improvements coming surprisingly quickly. (The challenge is to focus on the positive behaviors and not spend your energy criticizing the negative ones.) We even use it on each other. One could, for example, praise one's spouse for putting the toilet seat down (which has never been an issue for us, BTW; I'll keep the real ones to myself). Something like, "I noticed that you put the seat down, and I really appreciate that." It sounds corny, and when I say such things it feels unnatural to me, but it still works because it is sincere.
In the broader social arena, here is my suggestion: when you observe someone being civil, courteous, considerate, generous, kind, humble, or reasonable, load them up with praise. Point out the behavior and express your gratitude. Make people feel good about the things they do and they will do more of those things.
And the flip side: whenever someone does something objectionable, ignore it (insofar as it is reasonable to do so: defend against physical or verbal assault, but do it for the sake of the potential victim). Follow the rule of a Kingsman Gentleman, to wit: "A gentleman never reacts to rudeness. He pretends he doesn't recognize it and moves on like it never happened, because it never should have." Same goes for gentlewomen.
That's it. Praise desirable behaviors, and people will exhibit those behaviors more frequently. If we can interact with each other in a constructive manner, we can accomplish anything.
Thank you for reading! I sincerely appreciate it.