How to write plot

“I have a great book idea, but I have no plot.”

I hear this pretty frequently. Most new writers seem to think that plot lines are supposed to spring into their heads fully formed. Then they feel deficient when they come up dry. But plotlines rarely appear out of the blue – and never fully formed. More often an idea is nothing but a world, a character, a single scene, or a mere image. We must take these fragments and grow them into stories.