I want to write a fantasy book but I have NO ideas. please help?

I want to write a fantasy book.. Kind of like these books. Narnia , Inkheart , Fablehaven. Something like that. But i don't have ANY idea's. Anyone have any suggestions for a story line? I origanlly wanted to write about a girl who could turn into a wolf but people thought i was ripping off of twilight so now i want to do a fantasy. Any idea's?