FREE your imagination, give it permission to wander.
Ideas come to me all the time. From small details of the plot, to the characters to the scenery. It's like a really rough dream sequence that has no regard for the time or place of its arrival. I've gotten ideas in the shower, at 3 AM, coming or going places, while running errands, watching a movie, reading a book, drinking, listening to someone talking... the brain never stops creating and imagining. You ask yourself "what if" a lot when you're a writer and you allow yourself to answer, to truly imagine whatever images, people, settings and phrases come to mind. These initial ideas become the building blocks of my stories.
I cannot force ideas and I don't need inspiration to write. What I mean is, I can't sit down and say I'm going to plot out a book...but I can free write in order to build on my original ideas. I also don't need to write at a particular time or feel a certain way to write. Because I plot beforehand I know initially where the scene and books are going, therefore don't need inspiration to write them. I don't allow pre-plotting/outlining to be a crutch to writing. I listen when additional plot points or new ideas come along, this to me is as organic as it gets. I am not good and just writing and not thinking. That's why in yoga I have a hard time bringing my brain to a calm and relaxing point, there is always something or someone shouting at me to do something.
A tool for plotting I've used is courtesy of Alicia Rasley called Outline Your Novel in 30 Minutes. I used this when I outlined my urban fantasy novel. I had an idea of a loose plot before I started so this helped greatly and I used her outlining tips to flesh out the story. Once I have a pretty good outline, I plot all the scenes (or the major scenes) on the Traditional Plot Storytelling Story Board, created by Carolyn E. Copper in 2008. The reason I use this as a tool is because it goes through the stages a story arc contains and becomes my check off list.