Here's the important part of the OP:
"So, I'd like to hear about any rules you've had that now, seem a bit funny!"
The only standard offered for judging rules silly is rules that posters have personally had in the past and now find it silly that they ever thought they needed them. This is for each poster to decided for his or her self. There is no judgement of other peoples' rules being offered.
When speaking of various forms of non-monogamy...it ain't poly if you're just fucking around.
While polyamory, open relationships, and swinging are all distinctly different approaches to non-monogamy, they are not mutually exlusive. Folks can, and some do, engage in more than one of them at a time--and it's all good.