Writing for an audience

So most of us writers want to write to share their stories with others, but how do you go about deciding what audience you want to reach? Do you let the story tell you, or do you sit down with a specific audience in mind?

Me, I like to write the kind of stuff that I like to read, and that varies a lot. See, it's not easy. However, I've noticed that as I have matured as a writer, I have focused more on the Young Adult age group. I think it has to do with my fascination of Teenagers, and the many changes they are going through. Example, Graduation. It is a very scary time for most teenagers, as it signifies their first step into adulthood, but it also is exciting for some as its the moment of freedom. I like this dynamic because it plays so perfectly into interesting drama.

Teenagers are also going through developmental changes as well, such as learning who they are and what they want to make of themselves.

Not to get off track too much, I want to know how you go about deciding your audience?