I've written before about how I start a novel, how I get going. Situation.
I do think Patrick Ness's idea that a good idea for a novel will attract other ideas is helpful. It highlights one thing that I think confuses a lot of novice writers: one idea is not enough. It's not, usually, near enough. When people come up to you at a party and say, "I have a great idea for a novel" they might as well be saying, "I saw an interesting bird today."Birds are everywhere. So are ideas. You have to be able to develop an idea and one way to do this is to push deeper into it, creatively develop it, and other ideas will come out of that first idea and help you develop your story.
For me, I need a little more than an idea to get started. I need a situation. For example, an idea might be that aliens invade the earth. That's not really a situation yet. A situation makes it more specific. Telepathic aliens invade the earth; they're so advanced that they conquer it in ten seconds. That's a situation. Now I develop that.
One powerful advantage to working from a situation is you can keep coming back to it to focus your story. Think about it as you wander your way down the narrative path. It's where your story comes from. What does this mean to your characters? How they react develops not only the story but the characters. What do they want because of their situation? What's at stake? All these kinds of writer questions come out of the origin of your story.