LPT: If you're ever in a conversation circle at a social function, keep an eye out for people trying to get in and get them up to speed

This feels like a common courtesy I don't see enough, particularly the second point. In a conversation circle, always try to keep your side vision open to people trying to find their way in. It can be awkward to try and find your own way in so giving them a spot tells them they're included then drop a quick brief on the conversation "We're talking about pineapples on pizza, good or bad" gives them context to jump in immediately.