A detailed outline, plus the Search function! My outlines are so detailed that they're color-coded. (Okay, this is slightly embarrassing.) For instance, in the outline for my newest novel "I Meant to Tell You," any subplot involving the protagonist Miranda's strained history with her future father-in-law is highlighted in red in the chapters that reference it. The subplot about Miranda's effort to expand her job is in blue in those chapters.... and on and on. So when the characters go off on their own and rip up my original outline (as they always do), it's easy to find the places that need changing.

I hope this helps. Thanks for being part of this AMA.