Narrative misdirection is a writerly trick of establishing false expectations in your readers, directing their attention to the wrong information and causing them to ignore correct information. It's an excellent way to surprise them, and has uses in nearly every genre, though it is a staple of mysteries.
J.K. Rowling happens to be a master of this technique. Time and again, Harry is certain he knows who the villain is, and every time he is wrong! Author and blogger John Granger goes into a great deal of detail about Rowling's method in his book Unlocking Harry Potter.
In my novel Never Gone, I also played with the technique in various places. For example, take a look at this excerpt from chapter 12.
Go ahead. I'll wait for you.
You're back? Excellent. Did you see how misdirection can be an effective tool to make humorous moments funnier?
I'll explain the elements of narrative misdirection by walking you through what I did, and why and how I did it.
1. Limited viewpoint. My piece is in first person. The only perceptions you have are Dani's. There's a good possibility that she does not have the whole picture. She very well might misinterpret the data in front of her. But it's hard for you, the reader, to know that because I've removed other sources of interpretation by limiting the perception to only what she directly experiences, knows, or remembers.
Rowling uses third person limited. Omniscient narrators are a no-no in this technique. Your POV must limit perception.
2. Sympathetic voice and reader identification. Dani's internal monologue paints her as a smart, arty dreamer who's a bit shy. She obeys her aunt grumblingly, having thoughts of being put-upon with "stupid" assignments. Everyone has felt this way at one point or another. As a reader, you sympathize and take her side. You become willing to trust her judgments about what is happening and why.
3. Playing with expectation. Aunts are those sorts of benevolent authority figures we expect to play "the straight man" in any joke. I describe Cecily having a young child who is usually weaving through her legs or swinging from her purse strap, which cements a picture in your mind: maternal and focused there. I give you only the details that would support your existing expectations of "aunt."
4. Clues the character chooses to ignore. This is VERY important. The truth must be in the scene and there for the astute reader to pick up. Otherwise you just have very annoying out-of-nowhere surprises, not narrative misdirection.
I hint that Janie should be around, and that she had been playing a game called "guerrilla stealth"--a name that implies unexpected combat. I also point out that Aunt Cecily is the instigator of Dani ever leaving the cathedral nave and going into the quire. As a reader, you chose to ignore the importance because Dani does.
5. Details that capture your MC's attention. Does the beauty of Durham cathedral's quire really matter that much? Or the fact that the guide has an exotic accent? No, but as a reader you're willing to be pulled along in Dani's flight of fancy because of the style in this paragraph. I used a little writerly magic dust of pretty words and alliteration and imagery to momentarily sweep you into Dani's distraction.
Keep in mind you can't do pages of this kind of thing, but just a paragraph can be an effective "sleight of hand." It's like the "jazz-hands" dazzle that magicians use to point you away from the real action.
Likewise, drawing Dani's attention primarily to the guy she tripped over keeps you, the reader, from looking deeper into what her family members are doing.
6. Confirm misinterpretations. Both Aunt Cecily and Janie play to Dani's expectation. The aunt scolds, the cousin becomes "ashy pale" at the scolding. And it's no small scolding. The aunt's big reaction cements the misinterpretation as true.
7. Payoff, in which misinterpretations are clarified. This is one tiny detail you might be tempted to overlook. Do wrap up how the surprise really happened, because it's annoying to the reader when you don't. Rowling always does. In my little scene, it was a simple exchange: "You weren't supposed to tell your mum" and "you never said that." I didn't have to give a detailed back story of how or when Janie and Cecily planned their trick on Dani. The reader can imagine it easily enough. But I did need to make it clear they were in cahoots deliberately from the beginning or the payoff would have fallen flat, because readers just wouldn't buy it.
So there you go, a quick primer on the basics of simple narrative misdirection. In mysteries, of course, it gets considerably more complicated. The author must layer in clues and dazzling distractions, one on top of another.
How do you think you might use this technique in your writing?