Funny you should ask as I had a man ask me the same question today. The only advice I knew of to help him was to go to a swingers club and see if they could make contact with anyone. There are papers, places to advertise on the internet, and so forth but you never know what type of response you are got to get. Try advertising on lit there are good people here.
Every girl (but one) who has ever joined us for a 3-some was someone we met through swinging. I think thats an easier place for other women to get to know you both (especially what you both like) before going further.
We're also looking for a 2nd girl, and from what I've seen so far, it's difficult to find someone, so I had the thought today about a swingers club, and then I found this thread.
Does anybody have any suggestions about sites or clubs in Southern California?