Nothing to do with poly but it occurs to me that there are also de facto "rules" about other stuff in relationships besides sex/attachment. I think that things run smoother if these are actively discussed and agreed upon as well.
For instance, I am in charge of our finances, so they consult me before making major purchases to make sure the budget can stretch to accommodate them. (Unless they are paying for them out of their "play money" portion of the monthly budget - MrS handles that).
There are also agreements as to who is "responsible for" making certain that certain things are taken care of (cars, pets, home maintenance, etc.), and other household "division of labor" crap.
I am an introvert and don't tolerate "other people" (i.e. anyone but the three of us) in my home very well, the boys are generally very good about respecting this but do occasionally invite friends over. The, fairly recently negotiated, understanding is that if they invite people over then they are responsible for playing "host" - I will, of course, be civil to their friends but can remove myself from their presence if I need to (by "taking a nap" or "reading in bed"). If this became a regular occurrence we would probably need to negotiate a "frequency" clause about how often they could bring people over. I can suck it up for a day or two here and there but having my routine upset on a regular basis would be dangerous to my mental health!
Me: poly bi female, in an "open-but-not-looking" Vee-plus with -
MrS: hetero polyflexible male, live-in husband (22+ yrs)
Dude: hetero poly male, live-in boyfriend (3+ yrs) and MrS's best friend
Lotus: poly bi married female, "it's complicated" relationships with Dude/JaneQ/MrS (1+ years)
+ "others" = FBs, FWBs, lover-friends, platonic G/BFs, boytoys, etc.
My poly blogs here:
The Journey of JaneQSmythe
The Notebook of JaneQSmythe