To read, read, READ! And Always have a notebook with you, to write down the ideas that pop into your head. Or else they’ll disappear!
I think you have to have patience and collect ideas about something you’re really passionate about. Characters you want to talk about and that readers would want to read about. Then collect ideas for places in the book — look at photos and books about different places for inspiration. Then start collecting little things about the story and background… until you have a chest full of ideas. Then you can start writing the plot of the story, based on your ideas. When I write, I don’t want to know the ending when I start — but you may find that as you write it, soon you’ll have 20-30 pages! And the story sometimes tells itself after that.
– Cornelia Funke, writer of InkHeart, The Thief Lord and Igraine the Brave.