Scott Adams supplies them:
A conversation, like dancing, has some rules, although I've never seen them stated anywhere. The objective of conversation is to entertain or inform the other person while not using up all of the talking time. A big part of how you entertain another person is by listening and giving your attention. Ideally, your own enjoyment from conversation comes from the other person doing his or her job of being interesting. If you are entertaining yourself at the other person's expense, you're doing it wrong.
You might think that everyone on earth understands what a conversation is and how to engage in one. My observation is that no more than a quarter of the population has that understanding.
I think of it as a friendly tennis match. There is no attempt to score a point or win a match. There is merely the enjoyment of each other's company, an open-ended engagement that should and does lead nowhere, and an eagerness to play. This facet of behavior - playing - is in many ways, as I argue in Intimations Pursued, the highest expression of human freedom. It is also the highest expression of civility. We need more of it. And the blogosphere - at its best - achieves this.