Mistress Matisse, a columnist on kink and poly relationships for Seattle's The Stranger, has some useful advice about dealing with your partner's other partners (POPs) -- especially if they're not your cup of tea. Besides honest communication and "no bad-mouthing," she explains her personal approach:
I do have a strategy around preventing negative feelings from happening in the first place: not too much, not too soon. Yes, it's nice to meet the people your partner is dating. But some polyamory literature strongly suggests spending lots of quality time with your POPs, on the theory that it makes them less emotionally threatening. Phrases like "poly family" -- a Charles Manson-ish term I detest -- are tossed around, implying everyone should want to all hang out together. One gets the impression that poly people are damn-near obligated to welcome new POPs by love-bombing them like a Moonies recruit. I disagree.
. . . Once I'm used to the fact of the new POP, then I get to know him/her just as I would anyone else: slowly, organically, without any assumptions of intimacy. I think feeling that one must immediately like the new person as much as one's partner does is what breeds resentment and then dislike.