I play the "what if" game to help me, but I also do something else: I remind myself of all the things I'm afraid of in life. When I come up with a plot that addresses my own fears, it tends to be a stronger story.
Even little fears can help me come up with something. For example, I'm terrified of ants (I know, lame-- but they attacked me as a kid, so it's a psychological thing). Writing a story about killer ants sounds like a SyFy channel special, though.
So I dig deeper. Seeing a single ant on the sidewalk doesn't faze me. It's the swarm that gets me. The writhing mass of tiny bodies that move as a single organism, crawling up my legs, biting me everywhere...I'm literally cringing as I write this.
Basically, behind my simple fear of ants is a fear of thousands of malevolent creatures acting as one for their own nefarious purposes. How do you defeat a swarm like that??
And voila. That's a fear I can use in my writing.
So, my friends, what are you scared of? What's the real fear behind the simple object? Have you written a story that involves one of your fears?