One time, I had my writer's net open as I stood at a bus stop. Three people in a row stopped by and either talked to me or gave me something like an extra bus token. That led to another story idea. A writer's net is a state of mind. If you're mentally searching for a unique thought process, explanation, or history behind something you see in your world, you'll find an idea.
You can also flip to a random page and find a line. Use some piece of that or an idea there as a jumping off point for a story. Say you find, "The lions were watching." Write a story about omniscient lions overseeing a world or anthropomorphic lions on a world of anthropomorphic animals or something like that. Ask yourself the question, "Why are the lions watching? What are they watching?" If you're using a literary piece, you can allude to it in your story.
Search your world for story ideas, for something strange or interesting going on around you. Then start asking yourself what could really be happening in another world and why. Live life like a writer, and you'll find an endless supply of subjects on which to write.