I had a reader question that coincided with something I'd been thinking about, so I'm going to talk about ideas. Not where to get ideas. If you're having to ask where you can get ideas, then maybe you're not cut out to be a writer. Every writer I've ever known has had far more ideas than could ever be written in one lifetime. Ideas are everywhere, and they come constantly. The hard part is turning ideas into a book, and that's what I'll talk about.
The first trick is figuring out which ideas are enough to sustain a story. Not all of them are. A story needs conflict, and the longer the story, the more complex or strong the conflict needs to be. A novel needs a conflict that isn't easily resolved, that may be able to change or grow and that will affect the main characters on multiple levels, both internal and external. Dealing with this conflict should require the characters to make some serious choices that will change them in some way. When evaluating an idea, think about the potential for conflict and how the conflict might be resolved. If the conflict could be resolved if all the main characters just sat down and had a conversation (and there's no good reason for them not to have that conversation), then you don't have the kind of conflict that can sustain a story.
A novel also involves a lot of events. A good way to see if there are enough potential events to flesh out a novel in your idea is to make a list. See if you can come up with a list of at least twenty events that are inherent in your story idea. These don't have to be entire scenes -- several events could occur in one scene -- and you don't have to develop these events into one scene, but you need to figure out if stuff can happen.
But if your idea doesn't contain all the conflict or events you need to develop a story, that doesn't mean it's a useless idea. I often find that two different ideas may merge to create a solid idea. I have a lot of ideas floating around in my head at any given time, and every so often one may come to the surface and I'll think about it. I may add something to it when I think about it, and if it's still not "done," then I'll let it go back into the general mix. That's where ideas may collide or merge with each other and turn into something I can build a story on.
Ideas also need some input. Research can give you the kind of input that will add flesh to an idea. Even if you're writing about a subject you know, research will help spark additional ideas. Read about the setting -- time and place. Read about business types or careers related to your story. Read memoirs or biographies about people similar to your characters or who had to do the kinds of things your characters may have to do. I often find myself reading about historical situations even for books that will be in a contemporary setting, since history does tend to repeat itself. A war, conflict, crisis or other event may have parallels to something in my idea, even if it's on a much smaller scale in my story. You can also research elements that show up in a story -- music, art, various cultures, food, clothing, technology, etc. This kind of research may help you find sources of conflict or ways to add layers to the conflict in your basic idea and may give you ideas for more story events.
Even if you've got an idea that can sustain a story, turning an idea into a novel takes a lot of work, and that's what I'll talk about next.