I'm in the earliest stages of planning out my next big novel and it's a huge one. Getting my head around it has been quite the task. I've let the story circle around itself many times since I first conceived of the idea nearly a year ago and I finally think it's clear in my mind.
Some books are like this for me. There isn't immediately a clear path through the story. I have to rummage through the wastelands a bit before I find right cast of characters to fit the right series of events to tell the story I know I want to tell.
When I was a kid, I always traced coloring book mazes with my finger before putting the pencil to the paper. Sure, I could've erased if need be, but it always left a smudge mark. This habit has followed itself into my work. I've written enough books to become fully aware of the many pitfalls that lurk ahead of the first page. I find that playing the story out in my head a few times allows me to explore the world of the novel and discover dead-ends before I hit them.
I never really plan the entire book. It's more like placing trail markers along the way. My notes are there as a strong suggestion to follow. They let me know when I've wondered off the trail. Not that I can't keep going, but at least I will hopefully proceed with caution and a good sense of direction.