The main suggestion I would make is to serve as a model for civility by being civil oneself. When I am responding to a post, I typically begin my response by writing “Thank you for your post,” or, if this represents my genuine feeling, “Thank you for your thoughtful post.” This is not so complicated; I have never even once been put into what is referred to as “Facebook jail.” But I am surprised how many of my Facebook friends report that they have been temporarily thrown off Facebook, often multiple times. Something about engaging on these platforms seems to encourage disrespectful language.
I also look for opportunities, where this is genuine, to state in a post that I have been persuaded by someone’s argument that differed from mine. And, not often but occasionally, I respond to a disrespectful post by writing something like, “Whoa, I really think you have gone too far here,” but nothing stronger.