We need our Writer's Intuition throughout the writing process, starting with choosing ideas. Notice I didn't say finding ideas. Finding ideas takes curiosity and good observation and a little imagination. Finding ideas is downright easy. Choosing which ideas are worthy of being written is a little harder.
That's where Writer's Intuition comes in. From all the jumble of ideas battling in your head, you'll find the one (or two, or three...) that really lights a spark for you. The idea you just have to write. The one you know won't leave you alone. That's your Writer's Intuition talking. Listen to it. Even if it seems like that particular idea has already been done to death. Even if that ideas not the next "big thing" you've been hearing so much about. Even if someone tries to tell you that no one will want to read that kind of story.
Trust your intuition. Just make sure you have something uniquely yours to bring to the old ideas. Make sure that your passion and excitement for the story shine through. Then it won't matter what's big in the market right now.
Choose the idea that you are aching to write, and a great story will be just around the corner.