“If you’ve got a message, send a telegram.”
Keep this old Hollywood saying in mind as you write. Readers have no patience for lectures, so if you’re writing in order to spread a message rather than to tell a story, they will lose interest fast. And even if you aren't trying to write a sermon, themes can be poison for the early drafts of a story. If you start writing with a specific theme in mind, you'll be temped to wrangle your characters’ decisions to fit that theme—turning them from human beings into something abstract, symbolic, and boring.
But stories have to be about something, right? So how do you incorporate a theme without annoying your readers and flattening your story? Here’s how: Don’t let the theme guide your story; let the story guide your theme.
When you're starting out your story, don't worry about the theme. Most stories are about a character solving a problem, so if you want your story to ring true, that is where you have to start as well. Focus on the dramatic question—the problem that drives your story’s plot. For example: “Will Captain Ahab get the whale?” “Will Harry Potter find the Sorcerer's Stone in time?” What does your character want, what obstacles do they face, and what’s at stake if they fail? These are the essential questions that keep the reader turning the pages.
However, even at this early stage, there's a strategy you can use to help yourself incorporate a theme later on. Try to base your story around an ironic contrast. You can write about about a character who is completely unsuited for the challenge they’re facing—like Frodo Baggins, a tiny hobbit tasked with saving all of Middle-Earth. Or you can focus on characters that are opposites of each other—like Scully and Mulder on The X-Files, a skeptic and a believer. The meaning of your story will arise naturally from these contrasts.
Now that you've settled the dramatic question, it's time to think about the thematic question. This is the dilemma at the center of your story that helps define what your story is about. I say thematic question rather than theme because a compelling theme can't be boiled down to a single statement, like "greed is wrong" or "teamwork is good." These aren't dilemmas; these are just morals, and they will bore your reader. Similarly, your theme should not be an obvious question, like "Is it better to be good or to be evil?" Your reader already knows the answer to that one. Your thematic question should be a difficult choice between two alternatives. Lois Lowry’s The Giver has a compelling thematic question: “Is it better to live in a world of artificial pleasure, or to risk living in a painful reality?”
Since you already wrote your first draft, you should have a pretty good idea of what your story is about. Now you can begin rewriting your story in order to emphasize that theme. However, this doesn’t mean that you should state your theme outright—remember, readers hate to be lectured. Instead, try to tie background details into your theme, so the reader can pick it up without having it explained.
For example, in the prologue to Game of Thrones, a young lord ignores the advice of two experienced rangers and leads them to their doom. I don't mind spoiling this for you, because we never see them again. However, even though these characters aren’t essential to the story, they set up one of the major themes: "Is it better for young leaders to go their own way or to listen to the voice of experience?" Even though this theme is never stated outright, it shows up in the story over and over again until the reader can't miss it.
If you follow this example, your theme will shine through as though you planned it that way from the beginning.