Originally Posted by Kes
I have always told my partner(s) about an attraction as soon as it became more than a casual 'hey, I'm going to meet that person I told you about from yoga class for coffee'. IMO, blindsiding leads to much poly hell. That's why I have never done it, and always advise against it!
I agree with this, and this is how we've done it. It works for us to know more than may be strictly necessary, but that's better than being surprised.