1. Do know your audience
The reason there’s not a hard rule for what constitutes as “preaching” to the audience is because every audience is different. For some, any hint of an overt theme is considered preachy. But for others, they’re looking for stories with complex conversations about concepts and themes. So, know your audience and know what they’re expecting.
A philosophical book along the lines of “the shack”, is expected to have longer moments of conversation around the theme compared to a young adult fantasy novel that should be more action oriented. Know your audience and what they’re looking for.
2. Don’t break point of view with author intrusion
Point of view is a difficult concept, but the short version for this purpose is this: Everything in the story should be from the perspective of a character. This means that you should never throw in a paragraph where you’re talking directly to the reader about the theme (or anything else really). This is called author intrusion and will immediately take the reader out of the story. Instead, the theme must be shown in thought, action, and dialogue.
3. Do have only one theme
As hard as it might be, do your best to only have one theme per book. The goal when conveying the theme through a story is to show the complexity of the issue and present many different perspectives. Characters learning about, clashing over, and growing because of your theme should be a journey and should take time. If you try to shove multiple themes into one book, you will be forced to drag down the story and rely on talking to the audience directly which can come off as preachiness.
What you can do, however, is have mini themes that connect to the broader theme. Usually this looks like different characters learning a similar thing but in different ways. For example, if your theme is the importance of family, you could have one family member learning to appreciate their family, another member learning they can rely on their family, and another learning how to accept their family’s love. These are all different but connect back to the broader theme.
Of course, all rules can be broken, and that includes the one theme rule. But you must understand why the rule is there to begin with, to break it effectively.
4. Don’t have them “get it” right away
Your characters must make mistakes along the journey. If not, the resolution will not feel earned, and the theme will feel simplistic. You want your reader to be invested in the character’s journey, to celebrate in their wins and cry in their losses. But that won’t happen unless you allow your characters to not “get it” right away.
Let’s say your theme is about self-worth. So, your character is struggling with self-worth and they get a pep talk from a friend early in the story. If they suddenly accepted the peptalk and completely understood the theme, the theme wouldn’t feel earned. However, if they don’t accept it, it can become a seed that later bears fruit as the plot develops.
In the three-act structure, you can structure it like this:
Act 1: Disagree with theme, presented with problem
Act 2: Come up with solution that partially or completely goes against the theme, failure ensues
Act 3: Learns what the theme actually means and grow because of it, allowing them to overcome the problem
5. Do connect the theme to plot and character’s growth
The plot forces the character’s journey and the character’s journey moves the plot forward. Theme moves in tandem with these elements.
Consider creating a theme timeline and write out where in the book you’ll convey parts of the theme.
6. Don’t overgeneralize or simplify
A theme can be relatively simple, but even the simple theme should be properly explored. When you reduce a theme to generalities, the reader will merely roll their eyes. However, if you dive into the different facets of the theme, it will feel fresh even if the concept has been explored countless times.
7. Do show both sides
Having everyone agree on a topic is boring and uninteresting.
For example, let’s say your theme is on the dangers of pollution. If you get your characters into a room and they talk about pollution, a boring conversation is one where they all say a variation of “pollution bad”. Now having a character who loves pollution itself would be unrealistic, but people do have different values. Maybe some characters think there’s nothing they can do about the problem, so why bother. Other characters see dealing with pollution as too expensive. And others simply don’t think about it at all. Having these characters get into a room and discuss/debate/argue with each other is way more interesting and moves the plot along.
8. Don’t have over eagerness about the theme
One of the biggest causes of people feeling like you’re “preaching to the audience” is when characters become overly eager about the theme. This creates a feeling of fakeness or triteness.
For example, let’s say your theme is on the power of forgiveness and the main character has someone talking to them about it. You should not have the main character get all excited about it. It feels unnatural for a character to go “yay, I can’t wait to go forgive people!” Instead, have them misunderstand, be hesitant about, disagree, or argue about it. Any of these are significantly more interesting to read than simple acceptance and agreement. An eager learner makes the reader feel like they’re being preached to. While the character might eventually agree in the end, it should be a battle to get them there.
Phrases you should probably avoid while a character is learning about a concept:
“Wow that’s fascinating!”
“I can’t wait to try that!”
“That makes so much more sense!”
“Really? That's amazing!”
“Why don’t more people know about this?!”
“You’re a genius!”
“Wow, you’re so right!”
Instead, keep the conversation interesting by having them ask a question, debate a point, or shift the topic.