Have done several. For me, it is best when you find consistent people that you are compatable with sexually (similiar kink levels), you get to know them what they like and you explore together. I guess there are 3 scenaios in my mind
First, odd guy out finding a couple. I was friends with a married couple for a couple years and we would play on a regular basis, it only got better over time as we got to know each other. But I was always the odd guy, and that made it less enjoyable for me.
Second, being part of the couple and finding a guy. I have done this with a previous GF. That was a very different experience, being part of the couple, rather than being the odd person that made up the 3rd. I enjoyed this scenario a lot more than being the odd guy for several reasons. We never found anyone consistent, but did have a couple really good experiences w people that we talked to a lot before we met
Third, 3 people decide to hook up. I have not done this, but it is not too appealing to me, unless there was a lot of communication before hand
For me, it would not be so conducive in the hobby, as it probablyy is not going to be a regular thing. In my expereince, the first time the group is together they are feeling each other out, and is not be as satisfying as subsequent sessions. Unless there was a lot of communication beforehand on everyones likes, dislikes, etc.
my .02