Really, it is whenever you are ready. I slowly started changing how I dressed at first and then cut my hair. I used to have really long hair and I cut it short. From there, I started to slowly tell people that I was close to that I knew would not have a problem with it. From there, I just told more people as I was ready and eventually changed my name on facebook and posted a status explaining it. Now that I have transitioned and I am read as being male all the time, I sometimes have to tell people and they get really confused thinking that I am transitioning to female. So, in a way you always have to come out, it is just figuring how how/why/when you want to do it.