When keeping a story straight, it helps to track information flow. Being aware of what each character knows helps minimize plot holes, maximize believability, and manage multiple points of view smoothly.

What you know

Everything. As the author, you should be aware of big, plot relevant secrets, world-building details, and the endgame. While there are occasionally details that you’re still working out, it generally pays for you to know as much as possible. The more you know, the easier it is to maintain internal consistency, keep strong character motives, plan your plot twists, and conserve your details.

What you know doesn’t always have to appear on the page. It’s often better if some of it doesn’t, to avoid info-dumping and over-explaining. However, if you know the nature of the information that’s held back, you can allow it to color the story. For example, if Alice’s secret is that she’s in love with Lucy, it may seep into her actions even if it’s never explicitly stated. If Alice’s secret is that she killed Lucy’s pet goldfish, that will affect their relationship in a different way. If you know that Alice has a secret but don’t know what it is, she may be cagey and evasive, but an opportunity to create subtext is lost.

What the important characters know

It’s in your best interest to keep track of what each individual character knows. This allows you to factor the information they have into their motivation, and to let it play a role in how they act. If you have a good idea of what each character knows, that means that characters are less likely to appear either clueless or omniscient when they aren’t supposed to be. It also cuts down on coincidences and  Random Acts of Fate™ a bit, because you know whether the character knew that XYZ was about to happen, and whether they feasibly could have shown up when they did.

It makes sense for a character to know about

  • Their own secrets.
  • Any event that they have personally witnessed.
  • Anything that another character has told them.
  • Anything that reasonably could have reached them by word of mouth, or that they could have looked up (provided that they have the resources).
  • The political set up and geography of any place they’ve lived for more than a few weeks.
  • How their most frequently powers and abilities work, even if it’s just a rough idea.

It does not make sense for a character to know about

  • Other people’s secrets, if those secrets could not feasibly have been uncovered.
  • Events that they have witnessed that are not public knowledge, and that they have not been told about.
  • Events that haven’t happened yet,(barring plot reasons).
  • How powers and abilities work, if they don’t use these things often or have just acquired them.

Other things to bear in mind

As a rule, once you’re past the beginning of the story, your main characters should be aware of almost everything that’s common knowledge. They should also know a number of things that aren’t common knowledge. The exception is characters who are uneducated, or who aren’t particularly clever.

What everyone knows

Know what’s common knowledge in your story. These are the things that characters can reasonably be expected to know. For example, if the existence of magic is common knowledge, no matter how taboo or socially unacceptable it is, people are unlikely to be shocked at the fact that magic is real. Anyone who doesn’t know about it comes across like they must have been living under a rock. Regardless of what the reader knows, common knowledge should almost never be treated as a reveal. Treating information as a reveal in-universe often gives the impression that the POV character has learned something new, which prompts the question, “Shouldn’t they have known that already?”

On the other hand, if something isn’t common knowledge, it is subject to reveals. It also should earn a bigger reaction from the general population, and is more likely to be regarded with interest, curiosity, or shock.

Common knowledge includes

  • Any events that happen in a public place.
  • Anything that’s taught in your world’s school system.
  • Recent history, provided that it hasn’t been suppressed.
  • Anything that your characters talk about openly, especially in tight-knit communities.
  • Anything that’s common sense, or easily deduced from other common knowledge.
  • Local geography, politics, and current events.

Other things to bear in mind

  • Common knowledge can be incorrect.
  • It’s reasonably likely that someone might not know a few things that are common knowledge. Meanwhile, it’s unlikely that someone without extenuating circumstances would be unaware of most or all uncommon knowledge.
  • It’s not rewarding to watch characters learn things that are widely known.

What the reader knows

This is the hard part. It would seem obvious that readers know what’s on the page. But when a book is detail-rich or densely populated with named characters, the reader can’t be expected to be responsible for remembering everything. On the other hand, depending on the nature of the story, plot twists, and subtext, readers may be able to riddle things out that aren’t written on the page.

You can reasonably expect the reader to know

  • Anything that they have seen happen.
  • Anything that has been said more than once.
  • Relevant information about major characters.
  • Relevant information about recurring characters who have appeared more than once or twice, especially if they’ve done something important or had a notable entrance.
  • The nature of any plot twist that could reasonably be deduced from the information you’ve given them—once the facts are out, expect a few readers to put things together before the big reveal.

You shouldn’t count on the reader to know

  • Events that happen off the page.
  • Characters who have only appeared once, or who have lingered in the periphery.
  • Minute world details.
  • Any magic concept, location, or minor character with a made-up name difficult for readers to pronounce. Many readers skim difficult to read/pronounce words and cannot be called upon to remember them at a later time. They’ll probably recognize the word, but won’t be able to give it off the top of their head.
  • Anything that has been mentioned off hand, but not treated like an important detail in-story.
  • Any plot-altering details that haven’t been mentioned. (Seriously though. I once read a book where the main villain was hiding a brand under his beard, which marked him as a criminal. Except the book never mentioned that he had a beard until that moment. Don’t do this.)

The best way to tell what readers know is to find a few beta readers. It can be difficult to track what readers are aware of, especially since there’s a fair amount of deduction and inference that goes on, and because some readers are better at filling in gaps in knowledge than others.