Using "I"

One way Catherine Farnes reaches the heart of teens is by writing in first person.  Teens have a narrow focus.  They see what's right here and now, sometimes more clearly than other people.  The present and immediate future concern most teens more than what's happening ten years from now.  Their horizons constantly expand, keeping their minds busy with today - which leaves less time for considering the past and future.

That's not saying teens don't plan and reminisce.  They do.  But to reach them where they're most comfortable, keep your writing immediate.

Teens are also focused on themselves, and I don't mean that in a bad way.  They need to understand themselves before they can make important life decisions, and books for teens reflect that.  A greater percentage of 1st person, journal-like books exist in the teen market than juvenile or adult.