One of my standard - and fairly true - responses to the question as to how story ideas come to me is that story ideas only come to me for short stories. With longer fiction, it is a character (or characters) coming to visit, and I am then obliged to collaborate with him/her/it/them in creating the story.
Roger ZelaznyOccasionally, there arises a writing situation where you see an alternative to what you are doing, a mad, wild gamble of a way for handling something, which may leave you looking stupid, ridiculous or brilliant -you just don't know which. You can play it safe there, too, and proceed along the route you'd mapped out for yourself. Or you can trust your personal demon who delivered that crazy idea in the first place. Trust your demon.
Roger Zelazny