First, decide what the characters are going to do, and then provide them with the characteristics to make it plausible that they would do it.
Characters should have a clear and plausible motivation, which explains who they are and what they do. You should try to convey to your readers your character’s emotional, mental, physical, social behaviors and traits.
What makes a fictional character live and breathe is a past, a background, because people tend to behave consistently with their background. The simpler you can keep those reasons the better. The way a character behaves is also governed by his body, his environment, his experience and his ideas.
What often escapes beginning writers is the fact that you will learn your plot from your characters. The plot grows out of character. Think about the characters first. The development of the relationships between characters is what creates the plot. Let them reveal who they are and keep asking yourself, “What’s going to happen now?”
That’s what a plot is, what characters do even if they shouldn’t. You have a wonderful resource in your characters. Let the characters create the plot for you. I have heard authors say if a character "takes over" the writer is not a writer, he has no discipline, no control. This is absolute nonsense.
Characters who refuse to do what you ask should be given a raise and a bigger dressing room. They’ve come from deep inside you. When your characters start to behave badly, it means they have become "real people" to you, people who won't bend just to fit the maneuverings of your plot. Maybe you “dreamed them up” but they are becoming your partners in writing your book. What do I do? I listen to them and write down what they say.
Your plot will become evident to you if you listen to your characters and watch them doing and saying things. Keep trying to move the plot forward. Go along from scene to scene because you want to find out what happens next and so do your readers. Listening to your characters and allowing them to help you plot is the most important Novel Secret.