The Fountain of Writing Ideas is probably located somewhere in the vicinity of the Fountain of Youth which is actually great...as soon as we find one we'll find the other and be assured of looking forever wonderful in our author photos. Until that happy day, however, writers must realize on other means to come up with the ideas for their stories. Some writers, mostly those just starting out, ask more established writers where they get their ideas and the answers can be both varied and farcical.
For my part, I always respond to people who ask me this by admitting that I took out a lifetime membership in the voracious readers club, having begun to read at early age (three or four, depending on whether it was my mother or my father who was speaking). I consumed fairy tales and folk tales and then, as I grew older, moved into Enid Blyton, then Nancy Drew, Hardy Boys, and when nobody was looking, into Perry Mason. Eventually, the Chief Librarian allowed me to progress into the adult section but supervised all of my borrows. Fiction remains my greatest love but I read non-fiction, as well. What this means is that I have a huge fount (that word again) of story threads I can draw from. It doesn't mean I write the same story, it means I can take an element from one story and create a whole new one out of it. Take The Hunger Games, for example. I have no idea if Suzanne Collins has read Greek mythology but perhaps she's heard of the story of the Minotaur, a monster kept in the underground rooms of a king's palace. Every year, two children from cities subject to that king are sent to him to be sacrificed to the Minotaur. The similarities are clear but, like I said, I don't know if Ms. Collins knows the story. If she did, she used a thread to create something new and fresh. So, read, and read widely. That's my first advice to anyone wanting to write. Don't just stick to one genre and don't just stick to fiction. Read widely.
My second piece of advice is to always carry some kind of notebook with you or have it beside your bed. For some reason, my story ideas tend to come to me when I'm in bed so I keep a pen and pad handy. Some ideas are junk, but some will be useful. At least, that's what I've found.
Some years ago, I read a news article about a Grenadian bishop who was arrested in connection with the murder of a young girl. I had no idea what to do about it but I cut it out and put it in my Mystery Ideas folder (yes, that's how I've labelled it, don't laugh) right along with all the other news clippings, magazine articles, and images of people and places which intrigue me. (You don't have to have a folder, an Ideas Box would work just as well.) It sat there for years and then, late last year, I finally decided to try my hand at a mystery and I pulled out my folder. The old clipping about the Grenadian bishop caught my eye and, now, voila, I've got "The Dead Bishop," a story that will appear in my upcoming collection of crime stories, Storm Warning. My advice here is, collect your clippings and don't worry if the story idea doesn't come right away. It's percolating.
But, if you're really stuck, and can't find your muse, there are also tons of writing prompt sites on the web, like this one and this one.
Btw, I updated my December post on premade cover designers and added a few more, so you might want to take another look.