Me and DP have been to a swingers club, had a few threesomes (one with a bloke who did stuff with both of us, one with a woman who only did things with me and one with a bloke who only did things with me) and a general party orgy thing. They were all great, and brought me and DP much closer. We have decided to stop it now for a while, as it was getting silly (most of our friends knew we were into it, and I kind of felt like I had to "prove" how liberated I was to them all the time, plus the orgy was when I got so drunk I couldn't remember which of our friends I had shagged, and I found that a bit embarrassing) but will probably start it again at another point in our lives.
It just kind of came naturally to us, we are both very comfy with our bodies and our relationship, we are both bisexual so no hangups about what gender the other person/people is/are, and we can both see sex as a separate thing to love. We have rules, eg no doing anything without the other person being there or at least giving explicit permission (eg DP went out one night to the pub and brought some bloke back for a drink, he came and woke me up and told me he had someone downstairs and did I want to come and see what happened, I couldn't be arsed coming downstairs, so he went down and had a little snog with the bloke and watched the other man have a wank, then he told me all about it the next day)
One of my favourite memories from the swingers club is talking to another woman about dresses and having a drink, and breaking off from the conversation to ask DP to please budge up a little bit as his legs kept hitting my arm as he was shagging some other woman! I loved the relaxed atmosphere, there was absolutely no pressure to do anything, and everyone loved the fact that I have a hairy fanny and was still lactating!
Of course we always insist on condoms, for all contact, that goes without saying, and either one of us can call a halt to things if we feel at all weird or anything. But generally it has been a great experience, which has enabled us both to learn more about ourselves, our relationship and other people. I have slept with about three times as many people since I got with DP than I had beforehand! (although not one of them has had that special something that DP has, which is a combination of love and knowing my body almost as well as he knows his own )