As a writer, this is the question I hear most often.
Wish I had a good answer.
Usually, when asked this, I end up looking like Bambi at the barrel-end of a shotgun. I stare, stammer, try to be witty. Stomp my hooves for a bit. But honestly? I don't know.
I suppose one could look at it as gathering my supper at a salad bar. I pick and pull and consider various leafy plot ideas, pile them on the plate of my mind, garnish them with what I hope is tasty style, top it off with a heaping dollop of my personality. My dressing of preference is humor, heart, and horror. Steaming hot jalapenos of plot twists really set it off. I know, I know, it's an unlikely combination of flavors, but hey! It tastes great at the time, even if it burns when it leaves.
Finally, I let my palate of imagination hunger for the best. I demand shrimp. I know it's hidden away in the refrigerator of my mind somewhere.
Not good enough an answer?
Okay. Most of my books start with an image that strikes me. Out of the blue. Then I take it from there.
A bitter farmer standing on his front porch, angry against the world, plotting revenge. The house's windows rattle behind him. Why? I wrote Godland, my forthcoming horror/suspense thriller, to satiate my hungering curiosity.
Neighborhood Watch, my suburban, paranoid horror thriller, was birthed by my snooty neighbor across the street who refused to ever speak, let alone look at us. And she always hid within a snug-tight red hoodie. Why? Again, curiosity drove me to crazy answers.
My forthcoming darkly comedic suspense thriller, The Secret Society of Like Minded Individuals, gave birth when my wife abandoned me on the "husband bench" at a large outlet store. I studied the desperately bored men joining me there, wondering what secrets they could possibly be harboring. The answers might astound you!
On the way to see my inlaws, we drive through a dilapidated town just over the border of Kansas into Oklahoma. Creepy and sad, painful to experience. I researched the town of Picher, Oklahoma. My findings will form a sprawling, epic ghost saga of how greed, ecological poison and the forces of nature destroyed a once prosperous mining town.
Dunno where this came from, really, but an image sprang to mind of a kindly, little ol' lady coming at me with hedge-clippers, smiling beatifically. My next novel. Somehow, someway, details to follow.
Actually, writing is good therapy, as well. My Tex, the Witch Boy trilogy started life as a miss-mash of my exorcising my high school demons along with the detailing of my recently graduated daughter's tenure in hell. The books grew from there.
So, those are my answers. Think I'll print it off, keep it in my pocket. Because, as I said, whenever anyone asks me where I get my ideas? I freeze, locking up like a guy at a urinal with twenty angry, full-bladdered men waiting behind him.