Simply put the heart of your story is that one line version of your book that when read aloud makes people go, "Ah, that's cool..." (Or cute. Or fun. Or exciting. Or interesting. Or romantic.)
Like: The hero and heroine must catch a killer but she's already been arrested for the crime and he's the DA prosecuting her. (Now that's cool. You can almost feel the ticking clock, feel the heroine's desperation, feel the hero's impotence as the trial date approaches and he knows he's prosecuting the wrong woman...)
A lonely workaholic hero finds a family when he must help the heroine come to terms with her child's death when they're made co-guardians of his infant half-brother.
That's heartwarming. It's uplifting when a lonely guy gets what he needs when he goes the extra mile to help someone else. We can also almost "envision" the sad heroine, suddenly forced to care for a baby, when her loss is still too close to the surface. We also know there's a baby who needs care. There's going to be floor walking and formula feeding and tooth getting. And we also know this guy is already put upon...yet he pitches in and does what needs to be done.
That one line for THE BABY PROJECT brings together all those different facets. But it also focuses the story so that I (as the writer) knew what I was working toward. Even though the heroine needed help to recover, the character who really needed help was the hero. He was lonely. He needed a family.
So even as I was writing a story about an overworked hero trying to fit the heroine and his half brother into his life, and the heroine's recovery, and the baby's adjustment to new "parents" ... I was also subtly working toward having the hero realize that he didn't want the life he had been working toward for the past 36 years, but he wanted the life Fate was handing him on a silver platter.
The heroine's story is a good one. It's solid and strong. But the real "heart" of the story is the transformation of the hero from the guy he is when the book opens...lonely, overworked, stressed...to a guy who is able to accept love in his life and hire a bunch of vice presidents to take over some of his responsibilities.
The heroine's story is a "thread" so to speak that forces the hero's story. The addition of the baby into the hero's life also nudges him toward change. But they're not the main story. The hero's story is the main story.
You'll have a lot of layers in any story. But the trick is to figure out which one is the most important. Which thread would get you the most mileage with readers?
To look at THE BABY PROJECT, you might think Whitney's story with the loss of her baby and husband might be the more compelling. But though Whitney is struggling, we know she's smart enough to know she needs to push through. Maybe not today. Maybe not tomorrow. But eventually.
Our hero, Darius, knows he's in trouble, but he responds to that trouble the way he always does. He will work harder. Readers know this guy is drowning and there's a good possibility he will go down for the third time because he's missing a few of life's puzzle pieces. He doesn't know how to be vulnerable. He doesn't know how to ask for help.
He's gonna drown.
So his story is the heart. Whitney's story is certainly interesting, but in the end the way it supports Darius's story is actually a more important function.
So how do YOU figure out your story's heart?
The best way to do is it by writing a one-line summary...It's a book about a hero and heroine who must catch a killer but she's already been arrested for the crime and he's the DA prosecuting her.
If you can't state your story that succinctly, then maybe you need to do some doodling. Think of potential conflicts. Potential scenes. Potential trouble. Do some doodling about your hero and heroine. Write out some facts about their lives. Their pasts. Their core beliefs. Their parents. Anything, until something makes your breath catch and you say...Wow. That's cool.
Because if the story you choose to highlight doesn't make your heart beat a little faster, doesn't make you say, Oh, that's cool...or interesting...or fun...or scary, then it's not going to hit readers either.
So take a minute. Or a few days. Or two weeks, as I sometimes do. And just think. How could I come up with a really cool book? Or a GREAT romance. Or a wonderful spin on something that's been done a million times like a marriage of convenience?
And then give yourself the gift of writing something that you really, really like. Something you know readers will really, really like!