Action is anything that moves the plot forward. Action is the story’s essence: it’s the stuff that makes the story a story. The action is the plot: without action, there would be no plot.
Action doesn’t necessarily have to be people running around, doing exciting things: in many books, sections full of dialogue or characters sitting down to think and decide what to do directly affect the plot. For the sake of this blog post, we’re going to call that sort of thing “action”.
Why it’s important:
Without action, there is no story. People would get bored pretty fast. If you were writing a story in which nothing important or exciting ever happened, not many people would want to read it. Action speeds the story up.
Filler is anything that doesn’t move the plot forward. Filler can be removed without changing the plot or the outcome of the story.
Filler can be lengthy descriptions of settings, useless conversations between characters, characters doing things that don’t have anything to do with the plot and/or going about their daily routines.
Why it’s important:
Filler doesn’t sound like it should be important, does it? But it is. People get overwhelmed by the action sometimes: every once in a while they need a break. Filler slows the story down.
Also, if you’re writing fantasy or sci-fi and you have to do some worldbuilding, you’re going to need some filler to flesh your world out. If lots of cool stuff happens, but doesn’t make any sense because the readers don’t know the rules of your world, they’re going to get confused and possibly lose interest. It can also be good in more realistic fiction to flesh out your characters’ worldviews, routines, and location.
Some great stories have a lot of filler (but keep in mind that that doesn’t necessarily mean it’s a good thing: even the best works have flaws). For example, in Les Miserables, there is an entire 4-page chapter about what one particular alleyway looks like.
A note, though: don’t add filler just to up your word count. Actually, it’s generally good if your story is shorter than it could be. Filler should have a purpose too, even if it’s just there because you want people to know this or that minor detail about your characters or your world.
How to balance them:
As a general rule, don’t start your story with filler. Start with action, get people invested in your plot and your characters, and then you can get into some filler.
Finding the right balance can be difficult. All I can really say is practice, practice, practice. Just write a lot and ask people for feedback. If they tell you your story is too boring, you probably have too much filler and not enough action. If they say it’s confusing, they don’t understand it, or it feels too rushed, you probably have too much action and not enough filler.
Tweak it by adding or removing filler or action, then have someone else read it. Get their feedback, and keep changing things until it works. Then go back and mark it up: find all the filler and all the action and find out exactly what the balance is, then try to emulate it in anything new you write.
This is a lot easier to do with short stories than with longer works. I’d recommend writing some short stories first to get your style etc. down before attempting anything longer. BUT some people start with long novels, or have no interest in doing anything else. In that case, I’d recommend perfecting a chapter or two before moving on to the rest of the story.