So, I guess I shouldn't only lurk but contribute too. I know my wife has had fucked three other men, and think she may be "forgetting" some too. None of these are very recent, we have been together 20 years, so unfortunately it's not a topic we often visit any more.
Here's how: Her first was a high school crush. It (or he) didn't last very long - safe missionary type sex according to my wife, but good enough to figure out that she loved having sex. Then pretty soon she met a much older guy who in addition to new positions introduced her to watching porn, light bondage, anal sex, facials and swallowing instead of spitting... The funny fact is that on the surface my wife was (and still pretty much is) a good girl, not a sl*tty type at all. So while her friends, who had started having sex earlier, had already had some one night stands etc, were mostly having vanilla sex with their high school/college boyfriends, she was being tied up, getting her ass fucked...
After being together about a year we took a little time-out. During those 6 months I know she had at least one one night stand (according to her with a guy with a huge dick but no clue what to do with it). However, I think there may have been a few others, and know that she left a party with her room-mate and a new guy and headed to their flat. Of course they may have just slept, but more likely she either had a ringside seat to watching her friend having sex or joined in and practised some girl-to-girl love too.
Later on she worked abroad for half a year. We only saw twice during that time. I know her fingers and a couple of vibrating helpers did the work, but there would have been so many chances for the real thing as well. She said she didn't but who knows. What do you think?