Oddly enough, the connection comes mostly from communication.     So, the most memorable experiences and encounters I've had have been with companions I've had amazing conversations with.  I've met some truly amazing people, over the years, and the more we talk, the closer we get, in some cases.

Of course, I have a few very fond memories of over-the-top crazy "romps" but even in those cases, they've mostly been with people I established a great connection with.