This one's pretty straightforward -- Bruce Coville was putting together a series of anthologies, I was invited, and I wrote stories for some of them, including Bruce Coville's Book of Ghosts: Tales to Haunt You.
I will say here and now that Bruce is the best, most painstaking short-story editor I have ever worked with -- Jane Yolen is second, so it's probably something to do with writing for children. This story was much improved by his editing, even if it meant doing much more work than I usually put into a short story.
Anyway, this anthology was about ghosts, so I did my usual theme-anthology thing of sitting down and saying, "Okay, what are all the obvious things to do? Fine, don't do those." With ghosts, that means no spend-the-night-in-a-haunted-house stories, no ghosts guarding a hidden treasure, etc.
Then, "What's inherent in the premise that isn't obvious?" Well, ghosts are usually earthbound because they have unfinished business. What might that be? How could I twist that?
What if the business isn't as unfinished as they think?
As for the obvious, the obvious thing is for the kids to be scared of the ghost, so what if they do the opposite?
So there we go. There's the story. And given that I love generic titles (e.g., "Science Fiction") the title was obvious, too.