Post #2 is right on the money. You can't expect to make things up out of thin air--you have to use your own experience in some way. That doesn't mean you can't be imaginative though.

As a teacher, I might write about school and students. But I might also include a student who was threatening suicide, just to add to the drama of a story, even though I don't have specific experience with that. The story would be written using a setting familiar to me, but with some other elements included that would add interest for the general reader.

The old adage is "write what you know". Any piece of writing reflects the author in some way so it makes sense to use that to your advantage. Use your background, life and experience as a base for what you are writing. What ignites your passion? What has meaning in your life? What experiences do you treasure (or wish you couldn't remember?) Start from who and where you are in life and how you got there and then Write!

Good Luck!