While writing, write down the ideas that pop into your head — even the dumb ones.
If you say no to any idea, you run the risk of offending your muse, and then your flow of ideas will come to a dead stop. It takes only a moment to jot the idea in the margin or add it to your list of ideas.
Sometimes if you "unwrap" a bad idea there's a brilliant idea hiding underneath. If someone else comes by while you're working, they may happen to suggest a tiny change that turns your dumb idea into the perfect thing.
It's happened to me plenty of times, and I've begun to trust that any idea that shows up is there for a reason, even if its value isn't immediately obvious.