Three tips to avoid subplot sputter-out

A recent library haul was eye-opening. Two of the four books had amazing voice, but the plots fizzled, in part because of what I'd call "subplot sputter-out." I've seen this ailment in contemporary YA more than other genres, and it got me pondering why that might be.

In analyzing the problematic plots, I found it helpful to contrast with a book that did succeed where the others failed. Because book three of the library haul was a winner: Drums, Girls and Dangerous Pie by Jordan Sonne...