My books usually end where they began. I try to bring characters back to a point that is familiar but different because of the growth that they have gone through.
I'm not really a plot writer - I'm more interested in the characters and sort of small events that propel the story forward.
I didn't 'decide' to write YA, per se. But every time I thought of a story, it featured characters 15, 16, 17.
I don't like to do too much psychological research because it might turn a character into a patchwork.
My first job is to write the characters as full and authentic people as well as I can.