The more I write, the more I find out about myself as a writer.  I started not knowing anything and fumbled my way through my first book.  As I learned and studied the craft (and poked around inside you head and others) I learned some things that helped me become a better writer.

I like to know how I think the book will end.  Key word here is "think".  My endings generally mirror my beginnings in some way.  So, I sort of know where my book is driving toward based on goal and conflict of my protag and the inciting incident.  This kind of sets up the dark moment and the climactic scene.  I outline what I "think" are my plot points, my emotional journey, and anything else I think I know about my book (which includes backstory).

For me, I have to be open to all the possibilities as I write.  I learn things about my characters that I didn't know along the way.  Things develop.  Plot thickens.

I have done a bigger outline for current WIP than I have with any other project.  However, I'm well into my first revision and things will change.  I need the outline, but I can't be married to it.