I came out as gay when I was 15, with the help of my then boyfriend. Growing up, I didn't see anything wrong with being attracted to other guys. It wasn't until I was in high school that people started talking about guys "coming out of the closet" and stuff (I had a very sheltered upbringing), and my boyfriend said it was a good thing to do. So we told people in our schools that we were gay and then we told our parents. It just made us more popular, actually...
I don't really see the use in coming out in some big announcement. I think it's more interesting to just kind of insert it into a typical conversation, like when people are discussing who they think are hot. That's how I let people I know I'm gay as an adult, anyway.
I suppose for trans people, you really do have to make an announcement about it at some point in your lives if you plan on transitioning, eh?