I know there are as many ways of doing poly as there are those to do it, but, my wife and I have rules that we feel keeps things as not awkward ( wow does that word's spelling live up to it's name) as possible. We are each allowed one "trial" date with each person, after that, the hopeful needs to meet the spouse. The only real criteria for me (or her) giving the go ahead is if I think I can get along with her OSO.
I know many people who don't like to hear about or met metamores, but my wife and I get very NRE giddy and want to talk about them. Plus if any of these relationships are going to last, everyone has to know and like each other.