For instance, if you're into romance stories, you've probably read so many guy-meets-girl novels that you've subtly programmed your mind not only to enjoy such stories, but to weave your own romantic tale. If you enjoy reading fiction revolving around Amish characters, then you've probably soaked up countless tidbits concerning the Amish. You could teach an Amish 101 course, or you could apply that knowledge to pen your own Amish tale.
Once, as I reviewed the stories I enjoy reading, I myself was puzzled at the range of genres in that collection. Sci-fi, historical, military... I don't enjoy all fiction within those genres; yet, certain stories from each particularly appeal to me. That's when I realized the connection: I call it "Totally normal people in totally abnormal circumstances." Certainly, not every novel or film fits this definition, but the ones I seem to enjoy most do.
For instance, in The Hobbit you have a totally normal little guy (hobbitwise, that is) who enjoys his peaceful lifestyle and wants nothing to do with adventures. His life gets flipped upside down when circumstances whisk him from his home and plunge him into distant lands and constant dangers. The same is true of Bilbo's nephew Frodo.
Luke Skywalker believes he's a normal kid growing up on a farm. In Luke's case, he does want more to life than farming. However, even he isn't ready for the new role thrust upon him, and he doesn't believe he's up to the job of defying an evil empire. Just like Luke, Dorothy Gale of Kansas lives on a farm and dreams of brighter lights somewhere over the rainbow. But, when a tornado actually carries her there, Dorothy lands in a totally abnormal realm and can return home only after many frightening experiences.
In my own novel, Gunner's Run, Jim Yoder is a typical son of a mailman from a typical Midwest town in the 1940s. However, when he tumbles out the open bomb bay of his B-24 over Nazi Germany, this typical young man learns to look to God as he makes a run for his life across occupied Europe. Similarly, my current work in progress plunges a normal American teen into bizarre events beyond his control. (This is an expansion of a series of short stories I once published in Focus on the Family's Breakaway magazine.)
Now, consider the stories most appealing to you. Can you pinpoint a common thread in them? (Something beyond "It was a good story.") If you can single out the elements that most tantalize you, then you've just crystallized the types of stories you should consider writing. Any thoughts to share on this?