As a performer you have secrets. Your secrets are all the things that are going to happen to your character in the story. As a performer you have power over this. You can manage how you reveal them. Use them to surprise the audience.
Think about what you do to make a kid jump. You draw them in by pretending to do one thing, and surprise them with a sudden change. You can use that in performance.
You need to do it like that because your audience is scouring the stage for clues, trying to guess what is going to happen. Even when they don't think they are, they are. They have nothing else to do! So you need to manage your reveals.
The way to do that is to draw them the wrong way before giving hitting them with the reveal. This creates a feeling of spontaneity. This is what spontaneity is.