For my write-up today on The Unwritten Rules of Social Relationships, I'll use as my starting-point something that Sean Barron says on page 300:
"Using lead-ins. By this I mean good conversation openers and phrases that encourage the interaction to continue. These are things like, 'That's interesting. Tell me more.' They also include paraphrasing (without repeating verbatim) what the person told you. For example, someone tells you that she feels sad because her mother died or that she is overjoyed at getting an A on her test. You could respond with something like, 'I'm sorry about your mother. I can tell you're feeling very sad. Tell me about her,' or 'That's great. I see how happy you are about your grade.'"
I think that there's something to that. In the past, I've had my doubts about whether saying "Tell me more" is a good social mechanism. I've envisioned myself responding if someone said "Tell me more" to me with, "Well, I'm not entirely sure what to say or what you're looking for..." I've feared that people would tell me that if I asked them to tell me more. Plus, I remember one guy telling me about his job, and then he closed the conversation with "That's all I have to say about that." So I wondered if I was right even to ask him about his job at the outset! Perhaps I should have asked specific questions, but ones that were open-ended. I don't know.
On the other hand, in a world that does not listen to me much anyway, I have felt refreshed when someone says, "So, tell me more about" such-and-such. And, when someone paraphrases what I say, that tells me that the person is listening. So perhaps there's something to Sean's advice.