Just recently I found some notes I had made when I first started plotting the storyline for my book The Eye of the Storm.
I had been on a visit to Lark Hill Place at Salford Museum. Lark Hill Place is a wonderful, realistic recreation of a Victorian Street. I remember I was looking in a shop window with a small group of three or four children when one of the girls stretched out her hand and said, "Oh, no! I think it's starting to rain!"
Sure enough, there were some drops of water on her hand. "Of course it's not!" I said. "We're inside a museum!" The next moment I felt a splash on my head. I looked up and realised that the roof was leaking Drip! Drip! Drip! I just stood and stared at it for a few more moments and thought, "What if..."
And so began the seed of an idea for The Eye of the Storm. A few months later I had completed a Victorian time travel story - with a VERY nasty villain!
"What if...?" It's such a good question to ask if you are looking to start a new story.