When I began with my first book, I jotted down a few ideas.
Then I started writing. By the time I got to chapter 5, the story had taken over, some of the ideas I'd had went right out of the window and I had no idea where the story was going until I got there.
I ended up using some of those discarded ideas in my second book but even then, they were changed and the book went where it wanted. As long as I remain logical, cause and effect, one event leading in a logical manner to the next...
Well, you get the idea.