Morethan2, in addition to NYCindie's excellent suggestion, I wondered if you were looking for something relating to a specific issue? It sounds like, perhaps, you are struggling with something particular, and we might be of more help if we knew what, specifically, you needed help with.
In regards to respecting time with metamours, and if metamours are close friends, it's varied a lot in my experiences. And, it means different things, depending on the relationship.
For example, I've got a metamour who is awesome, independent, and all around drama-free and great. When the GF and I would spend time together, there would be some contact--sharing fun facts, saying goodnight, checking in before we left on an adventure, etc. But, they were both respectful that it was time for her and I, and so it wasn't invasive. I had another metamour who was a huge fucking drama queen, and finally asked for limited contact between BF and GF when he and I were together, because all of her interactions were so dramatic and disruptive (and, eventually, the relationships all imploded because she was uncontainable, but that is another story).
As far as being friendly, I prefer to know all my metamours on at least a basic, this is their name, phone number, and they're not cheating on their spouse kind of level. Other than that, some have been people I've become friends with and enjoyed hanging out with, and others never pass the "we're dating the same person and can be civil in social situations" level. I've found that, aside from some basic information and confirmation everything is above-board, letting the situation and relationships progress works for me much better than hard-and-fast rules do.
