I've never felt the need to "come out" like it's this big thing. I just am what I am. People will figure it out eventually. I mean, how many people "come out" to their friends and family about being straight or monogamous? Why should I need to "come out" about being non-straight and non-monogamous? That's so last century.
When I do tell people about it, I tend to approach it casually. It just is what it is. It's amazing how effective that is. If you treat something like it's no big deal, people will be almost afraid to make a big deal out of it. It puts them on the spot if they do.
I talk about my girlfriend the way anyone talks about a partner. Some people will clue in that I'm also married, and if they're curious they'll ask if I mean my "girlfriend girlfriend" or my "friend who's a girl." [I was once asked if I meant my "legitimate girlfriend" which my gf got a huge kick out of... "Yay! I'm legitimate!"] I might get questions about it, which I just answer matter-of-factly, and let them process it.
I was poly before I met most of my friends, so I never felt this need to come out to them and worry about whether they would still like me. I figured, if I met someone who couldn't handle it, then they probably wouldn't be the kind of person I'd want for a friend anyway. The only exception is my bestie, and we've always had the kind of relationship that would endure any personal discovery like that.
I don't have a lot of family that I'm close to, so I certainly wasn't going to call up my aunt whom I've only met about 6 times in my life and be all like "hey, guess what!"
My mom and I were watching a Dr. Phil episode about non-monogamy once, and she made some disapproving comment about it. I told her "hey, I'm like that" to which she replied "I don't want to hear about it." I wasn't seeing anyone else at the time, so I didn't push the matter (see "no big deal"). I just kept bringing it up casually every now and then until eventually she got used to the idea. Now that I'm married and have a girlfriend whom she's met and really likes, she realizes that it's not this big bad thing. Actually, last time we talked about it, she even admitted that she'd never really been "into" monogamy either.
I've never actually told my Dad. We don't talk all that often and it's just never come up. See above about "no big deal." He's pretty cool though, and I doubt he would care or make a big deal about it.
Gralson: my husband (works out of town).
Auto: my girlfriend (lives with her husband Zoffee).
The most dangerous phrase in the English language is "we've always done it this way."