By now most of my close friends and some of my not close friends know. My friend who I used to play with bought handcuffs from a military surplus store and taunted me with them while we were out with a fairly large group of people.
And I think I told my sister while I was very drunk one day...

People have learned in different ways, but I've never just sat down and told anyone. A couple of my close friends and I tended to just hang out and drink and chat every few weeks last school term, and conversation would inevitably turn to sex. Then one day I was feeling more open that others and one thing led to another, handcuffs and other things were mentioned, and before I know it I'm bitching about the fact that I hadn't been allowed an orgasm for days. That one opened their eyes a bit! There was definitely some incredulity, but no big negative reactions. one guy just said 'so? that's cool.', and my other friend said that well, she was working on not judging kinky behaviour, and that she knew the problem was hers, not mine.

It's nice to have most people be at least peripherally aware that I am one kinky character, I can make a casual joke about whether or not the rope I own would actually be up to heavy labour, not have people ask why I have so many clothespins...

Over time other people have had small glimpses into that side of me, and I don't lie about things. If the conversation leads around to a point where I mention something kinky or something evasive the large majority of the time I admit the kink. No bad reactions yet.
I even got a nice laugh when I relayed that I'm only cuddly after i get a beating.