My very first bdsmy experience was with a married couple who took me home one night from a club.

They had been poly for some time and had established rules that helped keep all partners in the loop and consenting. Like once in a group relationship no one is allowed to have sex with people outside the group and it really helps keep the std's away. No one from outside the group is brought in without the prior consent of all the other members of the group regardless of titular distinction (dom/sub etc).

I brought in a few rules of my own...like I was never going to try to get one from the other and took great pains to avoid any and all semblance of such action. To me: He and she were together first and no matter what I wasn't going to take them apart. At first I wouldn't do anything sexual with them unless they were both present and then after a while it didn't matter if I was alone with one of them. Either way I always made it a point to try and make sure no one was left out.