Rules aren't needed so long as all parties involved are capable of discerning right from wrong, and remember to treat people you care for as if you honestly love or care for them. When applied to polyamory, that would include respect for all their partners.
Because not everyone will have the exact same ideas or needs in regards to what would constitute loving behavior or respectful behavior, it is important to at least talk with everyone involved (or somehow communicate) the things that entail loving or respectful behavior.
Some sort of acknowledgement that you agree with or can at least abide by others definitions of love and respect is generally good, because if it is not understood that things are agreed upon it is only going to mean that eventually someone is not going to be happy with another's behavior. Many times people become stressed about confronting each other about specific issues. Talking about this stuff isn't always pleasant, so if you are going to go through the hard work, you might as well make it worth it by discussing the specific behaviors that hopefully do not need to made made into rules because people are intelligent enough to not do or act in ways that are not considered acceptable behavior by others parties you are directly or indirectly involved with.
Hopefully everyone understands the most basic criteria for love and respect, as sometimes things are left unsaid for manipulative reasons. For instance, most people would consider physically stalking a partners's lover or friends, or hacking into their computer and watching or listening to them through their onboard camera/microphone without first getting their consent as not only disrespectful , but downright abusive.
so depending on the type of people involved with you or your partner, you might want to talk about what invasion of privacy means to you. You'd be amazed how some people might not think gripping someone's house, or hacking into computers and smartphones is just part of a healthy relationship.
ETA- the term I used "gripping" I mean in a completely differently way then boring guy's use of "grip" as I mean things like breaking and entering a house and planting microphones so that one could always hear or see what was going on.
It's fine and dandy to have a security system on your own house, in fact that may even alert to you to when the breaking and entering, but without consent I say it's wrong to "grip" a persons house or vehicle, esp without their consent, extra esp when it means breaking into a person's house, extra extra esp if they are a survivor of previous abuse. I don't want to even begin to explain the level fucked upness that things get into if a person does all of that, and then attempts to post in public, in subtle ways about a person's life where the details are most private in nature.