I like to spring it on people like it's no big deal. I'll mention something about my husband, later I'll mention something about my girlfriend, using the word in a way that doesn't sound like a bff... and then let them ask their questions and usually it gets straightened out.
I would never go past the first date without explaining my situation and relationship style. I'm not in the mood to train someone new on the ins and outs of poly if they're not interested in it on their own. I don't want to trick someone into liking me so they'll be less likely to leave when I give them the news.
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."