I used to be much more reserved about telling people how much I love tickling. Oddly enough, the first time I felt the need to tell someone was with my first girlfriend: I was getting really turned on, but she was unaware that it was anything more than playful for me; it almost felt wrong, her not knowing. I really wanted to tell her, to get if off my chest but also in the off chance that she'd like it too, or at least be open to incorporating it into our everyday stuff.
So, naturally, I didn't tell her.
The first person I told was my best (female) friend; she had known me longer than anyone else and wouldn't have been surprized by anything I said at that point. She was naturally supportive. Next I told my girlfriend's best friend -- getting closer to the target, but if she freaked out it wouldn't be as big a problem. But she didn't (she turned out to be just as kinky as me, although in different ways). So, finally, having opened up to two people that probably didn't care,
I told my girlfriend. Actually, we almost got in a fight because I couldn't believe how not-shocked she was. She treated it like the most boring news she'd heard that week.
Since that time, I've told anyone who might ask what I like, including my girlfriends -- then again, they pretty much know what they're in for by that time!