Here's something I've never understood. We've all experienced the situation where we're at the edges of a conversation at a gathering where we don't really know people. Maybe we've introduced ourselves; maybe we haven't. Either way, we're standing there, looking in, trying to nod along, but there just doesn't seem to be any natural way into it and all we want is for someone to notice us and talk to us! However, when we're on the other side of it, and we see people hovering at the edges of our conversations, we usually ignore them.
Of course, in this, as in all things, I am amazing, since I just worm my way into the edge of the conversation and then wriggle my finger and say, "Hey, can I break in?" and then they say "Of course!" and then I listen in until I have something to say.
But most people are not like me. Most people cannot do that. And yet, they deserve to be included. I'm not saying you have to be best friends with the random people who drift up onto the edges of your conversations. All I'm saying is that you should try to include them. Ask them their name. Tell them the topic of the day. Ask them what they think. If they fall silent, nudge them a bit. That's it. Very simple.
This is the conversational skill I'm best at, actually. To me, it's so patently obvious when someone wants to be part of my conversation. And it's equally obvious when they want to say something but don't know how, or when they feel like they're slowly being forced out of the conversation. In fact, I often find myself frustrated when someone is talking to me and they don't notice (or don't know how to notice) the person lingering at the edge of our conversation, so they never pause long enough for me to bring the lingerer up to speed. Sometimes I'll just interrupt my friend myself, but sometimes I can't do it, and I have to watch the lingerer drift away in silent despair. Or, you know, silent mild awkwardness.