There's the safe sex clause. That's a biggie and non-negotiable.
STD testing is also non-negotiable.
Telling the other about someone we're interested in as soon as we realize we're interested in them.
Keep each other in the loop about what's going on in other relationships. ie: The other week Possibility was more amorous than usual. I wasn't able to talk to Breathes about it until the next night. He wasn't happy about how long it took me to tell him until I pointed out that was the first opportunity we'd had to talk about things when we were both awake, coherent and alone.
Make sure partner is told when the relationship is going to a new level. (see above)
Make sure partner is aware of any upcoming dates so they can make plans of their own if they want to.
Introduce any new possible partners to existing partners as soon as practicle is non-negotiable as well.
We don't have a lot of rules. Some boundaries are dependant upon the partner as well. Breathes had one that I had to add 'no sex in our bed' and 'see her when you KNOW I'm busy with something else because I DO not want to be around her'.
Any boundaries you set should be so that the 'slowest' partner is comfortable with how things are going. Most boundaries can be changed or abolished over time as we get more comfortable with the situation or person.
I have to admit, I got super lucky when Breathes and I got together. He's someone who insists on protection always. He listens to my fears and concerns. He sticks to the boundaries as closely as possible, almost to the point of being anal sometimes. He is a problem solver but will let me think on my problem as long as I'm comfortable with it then come to him with the problem and any possible solutions I may have come up with.
I also got lucky with Possibility. He was poly long before we ever met so I didn't have to go through that awkward "I'm poly and this is what it is" conversation with him. He's teaching me the meaning of patience though, lol.
I was just sitting here, thinking, to see if there was anything else to add, when a different situation popped into my head where the solution we came up with might be a good one for you even though the problem was totally different.
When Breathes and I sit down to go over our budget he's the type that can see all the numbers in his head and be able to see where he went wrong in the calculations, etc. (I'm the same with spelling but numbers not so much) I'm the type that has to have the hard and fast 'evidence' in front of me so I can physically see where the problem is and how he arrived at the solution. Maybe this would work for you guys--when you see a problem write it down. Think about it for as long as you need to and write down what the solutions you've thought of are then come to him with paper in hand so he can SEE where the problem is and what you think would make you feel better. He can also write down what his solutions might be then the two of you work out which one might work best in that particular scenario. He might be able to actually SEE and HEAR what you're saying that way since his 'remembering' something in the heat of the moment isn't working as things stand now.
You know how to find me if you have any other questions