I guess for me the part of establishing effective communication with your partners is the "meta-communication" - the communication about communication.
It is, in my opinion, vitally important for you to get a very clear understanding of what matters to your partners. Don't be in any doubt whatsoever. Without this you are going to have a constant battle with yourself over whether you are doing right or not.
So, for example, if your partner doesn't care one way or another whether you kiss someone at a party, then not telling them when it happens wouldn't be a serious omission. If, however, that is something that is very important to them, then not telling them takes on a whole new meaning.
I really don't think there is a "one size fits all" when it comes to this issue - you have to really understand and know your partners' preferences and needs.
I would suggest that if you can't or haven't had that conversation with your partner(s) yet, then you are asking for trouble down the road.
For the record, I happen to think that this is a lot of what is wrong with "standard" monogamous society - the "rules" are these undiscussed, so-called "commonsense" thing that more often than not gets people into trouble. If couples would just talk about this, it would solve so many problems!
Please check out The Birdcage - an open, friendly Polyamory forum for all parts of New York State
"Listen, or your tongue will make you deaf." - Native American Proverb