Once in a while, our creativity needs a little push to get the flow of ideas starting again. Here is one of my favorite quick-start tricks:
Open a novel and relate the first sentence to what you're writing or would like to write. Here's an example: the first novel I saw on my shelf is "The Man Who Fell in Love With the Moon," by Tom Spanbauer (I haven't read it yet, so I can't tell you whether it's good). Its opening line is, "If you're the devil, then it's not me telling this story."
The writing project I'm about to start is a surreal comedy screenplay about a group of people stuck on an island. The idea the opening line gives me is to make one of these people very religious since there is, at least for a time, an "end of days" feel to the situation. My protagonist is an intellectual who is either an atheist or agnostic, so this would make an interesting contrast. The conflict in beliefs could naturally lead to some conflicts in action.
One more example: Carl Hiaasen is one of my favorite contemporary authors and I just bought his novel, "Nature Girl." Here's the first sentence: "On the second day of January, windswept and bright, a half-blood Seminole named Sammy Tigertail dumped a dead body in the Lostmans River." (Hiaasen never wastes any time getting his stories started!)
For my island story, my first thought was, "What if a dead body washes up on the beach?" But since this is a comedy that seems a bit heavy. However, it makes me wonder what else could wash up that might provoke conflict or move the story forward, and that's something I'll keep in mind as I work more on the story.
As you can see, the prompt is just a way to activate your brain cells--where it takes you often ends up far away from the subject of the prompt.