So, I'm not going to pretend I've got this whole thing under control, but, some days it just WORKS.
I had plans with a friend this Thursday, so I told Jason that I had plans that evening (I knew he wanted to see me) but I was free after dinner. He makes plans with a friend. It's not a "friend friend," he has history with her. But he really wants to talk some things over in private (i.e. without me around)-- and this is a time he knows I'm unavailable, anyway. He and I plan to meet up afterward (and if she's cool with it, she'll come along). She knows me, but we're not very close, as we've only spoken a couple of times. Today, I double check with MY friend (our plans were not quite confirmed, but mostly) and she apologizes, but says she forgot it was Halloween and she has a work party. Can't meet me.
Alright, so now I don't have a dinner date, and X is busy. I could complain to him, try to guilt him into breaking his date, or try to force myself along (which I've done before, not successfully). OR I could hope his plans get cancelled, and sit around waiting for him till the last minute. I really don't want to be "that girl," plus I'll only end up feeling resentful if his friend does show up (most times she gets caught up in work and cancels, but you never know.)
Instead, I text another girl who I really want to spend time with and make dinner plans with her. It's a mutual friend, so, bonus, I can include him-- if his friend cancels AND I feel like it.
Anyway, for those who are genuinely puzzled by how the whole poly thing can actually be pulled off, hope that gives a decent example! Oh, and if this just sounds like, "Oh, hey, you're not one of those women who jerk your boyfriend around....or refuse to let him see any other females alone...or have friends of his own...." (or change the gender roles around) Ummm, yeah, pretty much
Not saying I'm doing anything generous here