Many writers believe that if they can make their protagonist quirky or even flawed in some way, it will take the character from being flat to well rounded. For example, you could have your protagonist be a heavy smoker with a weakness for prune juice; a mad scientist who grows exotic green beans in the back yard for research purposes only; or a young woman who buys so many books she has only pathways through her apartment and has put herself dangerously close to bankruptcy. But quirks and flaws are not real characterization. They are not the thing that makes us care about a character or compels us to keep reading. They are only superficial traits unless they hold some relationship to, or involvement with, your main plot line. Not that your characters can’t be quirky or flawed, but those things alone won’t carry the story.
Another type of flat character is the one more commonly seen, the one who doesn’t have any flaws or quirks and seems to be simply in the story to move the action forward. He’s the stereotypical good guy and he’s doing everything a good guy is expected to do. He is handsome and brave and sexy and wears the white hat. Even if he wears a black hat there isn’t any dirt on it. He rides along throughout the book but it’s the action, not him, taking center stage. Maybe we’re supposed to feel sympathy for him because he got jilted ten years ago by the only woman he ever loved. But if the old love affair has nothing to do with the present action, it’s a torch we would just as soon he douse.
For a reader to care about a story, there has to be something at stake for each of your main characters, and whatever is at stake has to be directly related to the present story line. It is not only what that character might lose, but also what he might gain, for these stakes will drive him. They will motivate him. A character’s goals, desires, and fears should also be considered; these can create inner conflict as well as exterior conflict with other characters. Consider the challenges each character will face in achieving his goals and desires.
Scenes, even beautifully written, will not keep the reader’s attention if those scenes are filled with murky, shadowy characters who have no personal stake in the outcome and who appear to be there only as place holders to drive the action forward. We all love quirky characters, but remember that flaws and idiosyncrasies are only the icing on the cake. They will never be a substitute for the cake. To create truly “flawed" characters, start with what’s at stake.