The big one apparently happened when I was 5. I somehow had gotten the idea that at some point as they grew up boys became girls and girls became boys. I asked my mom how old I would be when I got to be a girl and I was apparently really sad when I was told "never". I don't remember any of that, it was recounted to me later in life. I also apparently repeatedly asked to be a fairy princess on Halloween (never got to be one) and asked for Barbies (also never got them, tho to be fair I was never forced to play with "boys toys" either, and somehow at some point I at least got a my little pony).
After that tho I never really gave any hints to anyone else, with one exception, until a month ago (I'm 33 now). The whole time I knew it myself, but was scared ->-bleeped-<-less to tell anyone, so lived in outward denial. I started cross dressing in secret probably around age 10, tho that came in waves - I'd dress for a while, then stop and tell myself I was wrong to do it, then started again, then stop, etc. Sometimes I'd shave my legs, but I was usually afraid of getting caught, so most of the time I didn't. I did keep my hair about halfway down my back from age 13 to this past july (I cut it because I was interviewing for a job that would've tripled the pay I was making at that time and wanted to do everything possible to try and get the job. Sadly I didn't get it, so now I have to grow my hair out again.) But I never got it styled in the feminine way I wanted to.
I did flat out tell my ex at the beginning of our relationship that I wanted a vagina. She just assumed it was a sexual kink and dismissed it. Jokes on her. When she eventually dumped me and moved out she left a bunch of clothing behind. Mine now, and it looks waaay better on me that it did on her :-) Which, brings up the most recent "hint" I gave to another person. Having recently relocated to another state and having made new friends, I recently went to hang out with one of them dressed in my ex's clothes. She told me "you look very metrosexual chic today. You probably don't want to hear this, but with a little makeup and a hair styling you'd make a hot woman." I wanted to tell her "No no. Please. Continue." Didn't tho. Not yet. But, I think she's figured it out, because ever since then she's been dropping a lot of hints, to the point of asking me about it without really asking me about it. I'll be starting HRT in a week and a half, and at that point I think I'll tell her.
Haven't quite figured out how and when to come out to anyone else though. I'm the last living member of my family, so I don't need to worry about coming out to them. And pretty much everyone I knew before september is 2600 miles away, and I probably wont see them again for years if ever. So, I guess for me coming out really wont be a big deal.