Ooh, foreshadowing is my favorite!
I’m going to be completely blunt, I usually just wing it XD I do recognize some of those techniques, though I’ve never seen them laid out like that.
My favorites are probably the name drop and innocuous statement. I use them all the time, and the object one occasionally. The symbolism one is fun to layer in now and then, but it’s really hard to pick up on on the first read. It’s awesome to leave it there for people rereading the book, but don’t count on it to foreshadow entirely.
The prologue and prophecy are overall dangerously hard to use and very easy to get wrong, just because of how clear they tend to be. Many people skip prologues, and though I don’t personally mind them, they should be a last resort. And prophecies can easily be cliche unless done very well.
Something important to remember about foreshadowing is that your goal isn’t to surprise your reader with the plot twist. That’s a bonus. The goal is to give your readers a fun mystery to piece together, clear enough that they could predict it if they paid careful attention. You don’t have to outsmart your audience, that takes all the joy out of the mystery.
Now, you often hear that your audience is smarter than you think, but for foreshadowing, I’d have to disagree. Your audience is taking all of this in for the first time and they don’t know which details are important and which aren’t, so you’ll have to err on the side of heavy-handed. (For me, personally. I tend to foreshadow too subtly, so it doesn’t make sense when it happens, though I think I’m improving there.)
Foreshadow an event at least twice, preferably three times. Scatter your foreshadowing as much as possible, and remember what each of your characters knows. Something might be obvious to a character, then you don’t have to mention it in the narration if you want to maintain secrecy. (Don’t overdo this, though.)
A great technique I figured out is making a piece of information or an object have a double duty. It should have a clear meaning/purpose/explanation right off the bat, but also a deeper one that will get dismissed because the reader will go with the most obvious answer.
For example, in The False Prince (You mentioned you read it, I believe) Sage rolls a coin over his knuckles. Initially, it was a way for the reader to see he was worried or distressed, and that purpose made sense. Later you find out the rest of the story.
Also, False Prince has excellent use of innocuous statements. I enjoyed that book far more on the second read because I could pick up on all the double meanings.
You can also use your POV to hide obvious facts. Readers will remember anything that seems cryptic or open-ended, so if you’re afraid it’s too obvious, you can make your POV character jump to conclusions and explain away the occurrence or statement.
This will only work if the explanation seems plausible and logical to the reader. Then you can introduce a nice bit of plain, straight human error to your plot. Even better if your character has earlier demonstrated that they’re very single-minded and that they’ll just dismiss anything that doesn’t conform to their worldview.
On the other end, if you want to call attention to something, purposefully leave it open-ended or uncertain. Readers will pick up on it, especially if you do that multiple times.
Sage’s ‘gold’ rock is an excellent example of this.
Also, Beta-readers are the only way to make sure you got it right.
In the best case, the mystery will start off unimportant, then it’ll grow to be bigger and more important as your characters gather information/as you drop in foreshadowing. If you make it too important, too early, it’ll just look like your characters are staring past the elephant in the room. If you’re afraid it’s too easy to guess, just reveal it quickly. Nothing is more annoying than a very obvious mystery being dragged out for a whole plot.
You actually have a lot of leeway in foreshadowing, because your readers are seldom focused on it. Actually, they shouldn’t focus on it, they should barely notice it in the best case. The perfect reaction to a reveal isn’t “Huh? I never expected that,” but more “Oh! I should have seen that long ago, it’s so obvious!”
You can actually play with this quite a bit. I actually had a character blatantly state what would happen in the future. (Relatively far future, in the next book.) and though my readers noticed, they’ve completely forgotten about it. Even though it was literally the most obvious thing ever. Anyway, foreshadowing is mostly just listening to your gut feeling.
Readers won’t notice something until you point it out multiple times, scatter the information, don’t wait too long with the reveal. Readers will remember anything cryptic or open-ended, so you can give the reader false explanations to distract them. Prophecies and prologues are risky. Your goal isn’t to outsmart your reader, but to make it possible for them to solve the mystery by themselves. Also, it’s pretty hard to mess up foreshadowing.
Hope this helps! Foreshadowing is overall very fun and one of my favorite parts of writing.
Without darkness, there is no light. If there was no nighttime, would the stars be as bright?