Oh... good topic... so many stories, but here are a couple of the good ones.
Communication - Before my wife and I really knew what swinging was, we were open to the idea of sex with other people. We were at a party where the vibe was moving pretty solidly toward crazy sex, if not outright orgy. So, naturally, we got up and left. We were in the car, driving home, talking and suddenly it was "Well, I thought you wanted to leave.", "No, I thought YOU wanted to leave." By the time we turned around and got back to the party, the mood of the party had shifted and the opportunity was lost. In reality that was probably for the best for a lot of reasons concerning the actually people involved but still, I always remember that conversation as one of the points where we realized we really needed to communicate better.
Say no - Fast forward more years than I like to think about. We're swingers. We've done some crazy stuff. We're at a club and have met a couple. The guy is clearly very into her. The lady obviously couldn't be less interested in me. The sex happens and it is not good. I'm left feeling pretty rotten. Never take one for the team, especially since my wife really wasn't that into the guy either, she was just playing for the sake of playing. We realized we needed to remember to say no when a particular match up doesn't work for us.
The worst person you can lie to is yourself - Fast forward again, more years than I'm comfortable with. We discover that several of our friends, including one incredibly hot younger (20-something to my 40-something) lady are also into the lifestyle or at least not adverse to it. So I ask her if she would like to hook up. To my shock, she says yes. We have a great time and decide to do it again. She is very clear - she has a wife, a boyfriend, a girlfriend and she can't commit to anything beyond friends-with-benefits / occasional fuck-buddy. I say that's fine. I say, I'm an experience swinger I can handle that. I say, I'm not looking for anything more. Every word out of my mouth is lie. I am totally crushing on this woman. I absolutely want more. Even when I admit it to myself, I pretend I can handle it. Crash and burn (you can find the whole thing the archives here).