Every story needs conflict, not just mysteries or thrillers. Romances need conflict, so do Sci-Fi novels, even Humor pieces and Mainstream. Not all of it, in any genre, is physical. Conflict can be psychological, mental, the tug and pull of opposing ideologies, man versus nature, man versus woman, man versus animal, man ... boy, man is contrary, isn't he?
As you write, and especially as you re-write, you need to be aware of the conflict in your story. Rarely do authors have to lessen the conflict. Usually, the problem is revving it up.
As you work on your story, here are some things to keep in mind:
As much as possible, keep the action on stage. As readers, we don't want to be told what happened. We want to see it occur. Whether that conflict is a physical fight, an argument, a debate, sexual tension, or whatever, let us live it along with the characters. Maybe it's hard for you to write about the subject or maybe it's difficult to get the dialogue right ... all the more reason for you to put it on stage.
As the story progresses, the problems facing the characters, especially the protagonist, should get tougher and tougher to solve. The tension should wind tighter. The conflict should become more important. Obviously, some problems will be resolved along the way, but don't be too quick to get your protagonist out of trouble. Just when he or she gets out of one situation and takes a deep breath, put them in another.
To do this, look at each scene and ask yourself, what could go wrong here? What is the worst thing that could happen? What would this character NOT want to happen? Then do it. Put your character in an even worse situation. Give him a conflict that he didn't expect. And when he maneuvers his way out of it, do it again, each time upping the stakes.
Go through your novel. Make sure every scene has conflict. One way to manage this is to look at each character as an individual, with his or her own story. No matter what the situation, no two people want the same thing. Whether the conflict is overt or hidden, it's there. Each character has an agenda, a backstory that affects the way they talk and think and react.
Your novel will also contain more conflict than just what is going on between the protagonist and antagonist. Layer the conflict. Doing that will make your secondary characters more interesting. It will enrich your story, give it depth.
Make your story more of a "big" book than just a one-dimensional plot. Build up, spread out, intensify the conflict. Just because your book is Mainstream, don't think it doesn't need or have conflict. Life would be pretty dull without conflict. And life is what you're writing about.
Do you try to keep your characters on a roller coaster ride? Do you take your readers along on the ride?
4 months ago