A writer on another loop posed this question (or I should say these questions). In fact questions like these are very common with new writers and I applaud her for asking.
So, let's take this piece by piece.
How can you make sure the idea you have isn't a waste? This is really a tough question but one that can be figured out with a little bit of research and an even greater amount of critical thinking. They key to this is be an avid reader. See what is out there on the shelves. Keep track of common trends you see in the writing. This might not be so much the bigger plot line but individual elements about the characters and what they do. For example, as you read through romances you will find that the heroes will almost always have that good side in them. They may be cold at first, but you certainly won't see them doing unethical things. Here's another one. While people having affairs may be something that happens a lot, and likely did happen a lot in the past, you will be hard pressed to find those characteristics in stories. Hmmm? What does this tell you? If your story is doing something like that, it may be a factor against you.
The other thing to do is really read through the submission guidelines and material for the publishers you are targeting. See what they are talking about. There will be hints here.
Finally, use some common sense. Think about your story. While it may be unique, is it really something someone will find exciting and want to turn pages on? Let's talk romantic suspense here. Would a romantic suspense told from the villains point of view be something we would want to read? Although an interesting approach, proabably not.
Can you query a synopsis? This one is no, until you become established. While you may have a fantastic idea in the story, we need to see the execution of it before we make a decision. Later on, when you become established and the editor and agent really know your style and know what you can do, writing "on proposal" does happen. Now, with that said, there are a few exceptions to this. I have seen new writers with some powerhouse agents sell on proposal, but those are really few and far between.
The second part of the question was whether you should wait until you have the first three chapters before sending it out. In this case, the answer really is, wait until the entire book is finished. Assuming you do have a great idea and query me, I will likely ask for the first three chapters. Assuming I like that I will ask for a full. Now here is the twist. My turn around time is fast and I expect the story to be back to me in a month. Of course, if you can write the entire story in a month and know it will be good, then go for it. The odds are, you can't. Other agents, if you send them a query may love it and ask for a full manuscript. If you don't have it, we really hate not seeing. I have seen several agents complaining about falling head over heels for a great story and then never seeing it.
Simple point. FINISH IT! There is no rush!
Hope that helps. L.T.
Thanks Pam Crooks for the photos.