I've read that people ask that question all the time. I've also seen book on the topic of generating ideas - or breaking through a mental block. From these tidbits I assume that the problem is out there, but I wonder "really?" Is it really hard to come up with ideas. I mean I get so many ideas for stories that I don't know what to write sometimes.
Take for example as story from the latest webNews. Richard Zimmerman, a cave dwelling loner in Idaho dies at 94. WOW! The obit goes on to explain that "Caveman Dick" has lived in his apartment complex of caves since 1947 - without t.v., a telephone, or electricity. The possiblity of stories from that man's life is so bountiful. Next story on the list announces lucrative summer jobs. Seriously. A job on a cruise ship! "Die Hard on the High Seas".
Ideas are all around us, we writers just need to know where to look and "how" to look with our imagination. We can even find ideas within our dreams (um... "Twilight"). I've had a few of them, though I have yet to make them into full stories.
The most common question I get now is "where did RABBIT SLAYER come from?" Sure you might THINK it was "Alice's Adventures in Wonderland" but the truth is the idea came from a song. Many years ago I found an MP3 clip of a song that was a parody of Elmer Fudd hunting rabbits. I thought "how cool would it be to see something like that in story form?" Then while taking a shower I fused the song with Carroll's book to get a little story for my daughter. The little story has now morphed into the book and series that I call "The Alice Chronicles".
My point is: ideas are all around us. We just need to look with our imagination - asking ourselves "What could I do with it?" There we go an idea is formed. Try this little exercise - go out into our local city square, some place populated and watch what goes on around you. What catches your eye - then let your imagination take over and create a snippet of a story showing that scene.
That is just one exercise I use to keep up the creativity. There are tons more. What exercises do you use to help generate ideas?