I like using epigraphs.  They're the quotes, songs, poems, etc., that authors use to preface or elude to what's upcoming in the next pages of the book.

In Denver Nights I used conversations from characters in the book (from various points of their lives).  I thought it was a cool approach as opposed to using someone else's material.  For the DN sequel, Arizona Mourning, I'm going to use poems written by the killer.  I think it'll be an effective way to give insight into the killer's mind...just a different perspective, you know?

Gerald Murphy was unveiled as the murderer at the end of DN, but was intentionally not developed as the story was about Alex, and somewhat about Jack.  I think it's time to peek into the killer's mind a little bit though.