There is a Tommy Wonder essay in The Books of Wonder that talks about misdirection that, I think, gets just about everything wrong. It starts off with a discussion saying we should call it "direction" rather than misdirection. His point being that we should focus on the thing we're trying to draw their attention to, rather the thing we're trying to draw their attention from. While this makes sense, it's also, essentially, just semantics. If you're "directing" someone towards something in order to take the focus off something else... that's misdirecting
He then writes:
[F]or our secret moves to avoid unwanted attention we must direct attention toward something else. From this it follows that we must have something else available at those times, something of interest. The more interesting this certain something is, the easier it will be to focus attention on it. The next time you wish to hide something, don’t think of hiding it, but rather think of what you can offer of interest in its place. Preferably this should be something thoroughly intriguing.
This is genuinely awful advice.
Rattling your keys in front of the audience so you can do your secret move isn't misdirection. Nor is it "direction." It's simply distraction.
Misdirection should be a secret action, but if I pull your focus to something "thoroughly intriguing," that's a very overt action.
Let's say you write something down on a card and fold it into quarters and hand it to me and I hold it in my right fist. With my left hand I bring out a bismuth crystal. I tell you that bismuth is the "bism" part of Pepto Bismol and that we can actually extract the element back out from Pepto Bismol caplets. This beautiful, iridescent, rainbow crystal is actually keeping you from shitting your pants when you have diarrhea. And just like it binds up your intestines to keep you from spewing brown gold everywhere, it can also bind up your thoughts to keep them from pouring out of the butthole of your mind, allowing me to catch a thought before it evaporates into the ether. I then "read your mind" and tell you what you wrote on the card.
How clever of me! When your focus was on the crystal I got my peek. And you had no clue.
The problem, of course, is that while you might not have seen me get the peek, you know your attention was directed away from the card with the word on it. If your attention is shifted away and then something changes: the magician knows the word you wrote down, the ball has disappeared, the card is in the magician's pocket. Well... that's all the explanation you need. You don't need to know exactly how it happened, just that there was an opportunity where something could have happened. That will knock something down from a miracle to a clever trick.
I'm going to give you some advice that has been very, very helpful to me in creating effects that I think truly feel like genuine mysteries to the audience:
Don't think about misdirection as being about the direction of someone's focus or interest. Instead, think about it as the direction of someone's suspicion.
If I tell you I'm going to sneak into your house tonight, the Tommy Wonder style of using misdirection to accomplish that task would be to set off a fireworks show so I can sneak in while you're distracted.
The type of misdirection I'm recommending is akin to climbing in the window while you're guarding the door.
An audience can feel it when their attention is redirected from their natural locus of interest. When we did the testing on card peeks, the worst performing one was the one that occurred when the participant's focus was drawn away from the deck and the magician.
What does it look like to direct someone's suspicion? Here's an example. When you use an impression pad, it can feel very clean and neat to have them write down a word, tear off the sheet, fold it up and put it in their pocket. Why wouldn't you do this given the pad allows you to? Well, one reason you might not want to do it is that now the pad is the only item in play that could offer a clue to what they wrote. Given that, your peek of the impression can't be awkward at all or else you're intensifying the suspicion on the pad, which is exactly where you don't want it.
But if you don't allow them to pocket their word—if, for example, you ask them to fold it up and let you hold it in your fist—their primary focus of suspicion is on something that's genuinely clean (your hand holding the paper). You're never going to do anything sneaky there, but that's where they would assume something sneaky would happen. So when you pick up the pad with your other hand, open it to the impression, peek the word, let a few pages fall over the impression, then set it down to write or draw on it—even if you do this awkwardly (which you likely will because you're doing it with one hand)—it won't seem strange because the focus of their suspicion is the paper in your other hand. They're waiting for you to try and get a peek at that. And when you never come anywhere near opening your fist to look at the paper, then they're at a dead end.
In this case, the folded up paper is the door they're guarding and the pad is the window I'm sneaking through. But that's an imperfect analogy, because if done correctly, they don't even know the window exists. All of a sudden you're just in the house with them.
By directing their attention with suspicion, rather than with interest, you get to use the power of their skepticism and distrust against them. On the other hand, if your focus is on directing their attention by focusing on that which is fleetingly interesting, you're just encouraging them to slough off the mystery by putting it down to mere distraction.