Like Hermione Granger, my answer to every problem seems to be to check the library. So with my sparkly new idea, I've been consulting other books, left and right, to see how authors tackled similar themes, issues, and characters.
Some writers don't like to do this. I know of writers who refuse to even read fiction when they're writing it. More frequently, I hear writers claim they don't want to read anything similar to the genre of book they're writing.
But I have found that reading books similar to the type of book I'm writing helps me to interrogate my own ideas and push them further. It also gives me a sense of what has been done before, what hasn't, and what works. Sometimes I do read something and think, "Wow, I wish I could have a plot like that." But of course I can't because A. someone else already has and B. my head works nothing like that. So I don't find myself copying ideas.
For example, my new idea has an element of romance, a genre I'm quite unfamiliar with. As I've been reading, I have yet to find a single book which starts with the characters already in love. Most romances start with the characters not knowing each other, a few start with the characters as friends. So I've been considering these tropes, the reasons behind them, and how I want to start the relationship in my own book. By the way, I'm a bit like a fish out of water when it comes to romances. Any reading suggestions?
I've also had the pleasure of reading THE FORESHADOWING by Marcus Sedgwick. I knew I had to read something by Sedgwick because he is the Author-in-Residence this semester at Bath Spa University. My classmates were really excited, but I knew nothing about him. I picked up THE FORESHADOWING specifically because it has an element similar to one I am considering for my novel*. And you know what? Not only did it ask a lot of questions of my sparkly new idea, it was a FABULOUS story. So exciting to discover a new author. So I went to the library yesterday to pick another of his books, and found a shelf full of Sedgwick. I restrained myself and only got two.
I get to meet him next week! Now I can't wait.
*I know I'm being cagey about my new idea and it leads to vague writing. Sorry. But I like to keep new ideas secret for various paranoid and artistic reasons.