Etiquette for poly people or for when interacting with poly people?

Ok, so poly etiquette can address two different areas; Internal and External etiquette.

On the internal front, how do we treat our lover's friend's lover? How do we deal with the frustrations that arise from having to deal with our partner's partners? When dealing with shared space, how do you work out matters of priority when both people want to have a lover over?

I will also address matters of politely interacting with non-poly people when you are and politely interacting with poly people when you aren't: How much is it polite to call attention to the fact that you're poly? If you're not poly, how do you deal with your sister wanting to bring her husband and her boyfriend to Thanksgiving? There can be awkwardness on both sides.

So whatever your question of etiquette is, feel free to ask.