So, when an idea pops into my head, I spend some time in my mind developing a rough form this idea, give it a bit of shape and some kind of path to work with. Then, I google it. I look over any other books with a like title, plot etc. How much the same are they, are they completely different, or did this author make a wonderful story out of this idea. 
  I woke this morning with thoughts on an idea that has been rolling around in my head. So, I rolled out of bed and shuffled to my computer to google this idea. Not only has someone taken this idea in a great book, but a whole series of books. Good enough that I'm interested in reading them myself. 
Back to getting the idea juices flowing I guess...