A great twist can make a story (think, would The Sixth Sense have been nearly as popular without people loving its?) but a poorly done twist can just as easily sink one (think every other M. Night Shyamalan movie that has been panned in the years since Sixth Sense).

The general advice I have when it comes to twists is only use them when it flows naturally in your story rather than being a planned gimmick. If you are trying to force your story to conform to a plan just for a twist, don’t do it. Ninety-nine percent of the time the damage you’ll do to your story will not be redeemed no matter how mind blowing the final twist is. Some gimmicks work, but more often than not a well-written story will beat out a mediocre but unique gimmick.

If you are planning part of your plot around a twist, however, some more specific things to keep in mind:

1. Make sure the story supports it. This is one of the major stumbling blocks that get many “twist-based” stories stuck. When the author starts becoming hyperfocused on their great twist, it often opens up the story to other plot holes. Sure, you can hand wave a lot of things in fiction if necessary, but when you start having readers question the very premise of your story (why would the aliens even want a planet that’s mostly water if they’re allergic to it?) you’re going to have a problem. If there’s no reason for the story to progress in the first place once you learn there was someone controlling it the entire time or it turns out a character is a turncoat, the twist isn’t going to protect you from criticism from readers left scratching their heads. Likewise, if your twist relies on other characters keeping information from one another, make sure they have a reason for keeping that information to themselves outside of “because the author said to” otherwise the rest of the plot can stop making sense.

2. Don’t make you characters seem like idiots. There is an ongoing joke that characters in Superman comics aren’t able to see that Superman and Clark Kent are the same person past a pair of glasses. At this point, it has simply become an accepted part of the storytelling along with the fact that no one ever really stays dead in comics. Unfortunately for those writing outside of the DC or Marvel universes, that level of suspension of disbelief doesn’t carry over to most other forms of prose. Where the people of Gotham may still not get that Bruce Wayne is Batman even though Batman for some reason disappeared at the same time as Bruce Wayne and he always seems suspiciously “away” when Batman’s out and about, readers are going to start getting a little annoyed when your character hasn’t put something together that it seems any reasonable person would have. You definitely want to have some sort of foreshadowing when it comes to a twist, but don’t offer enough so the reader has figured out the twist so far ahead of the character that the character seems dim for having missed the myriad of clues.

3. Foreshadow properly. As stated above, you don’t want twists to entirely come out of nowhere. If there has been absolutely no sign of anything nefarious happening, a twist that turns everything on its head can be just as annoying as a twist that was signposted way too early. Readers don’t tend to like being blindsided. Make sure there are some clues that foreshadow the ending. Just make sure they’re subtle enough so it make sense that your character has missed them without needing to throw in some sort of explanation about why they were uncharacteristically nearsighted when it came to an obvious twist. If some of your readers figure the twist out, that’s fine. You don’t need to try to trick every single reader. Readers like feeling smart, especially when it comes to figuring out where something is going before it’s revealed. You just have to make it difficult enough to figure out that 1) your character wouldn’t figure it out and 2) your reader doesn’t feel bored by the time they reach the twist because they figured it out ten pages in. So how do you foreshadow properly? It varies from story to story, of course, but some general tips to tread that line between blindsiding and boring:

• Place “big” clues early on. The earlier on you are in the story, and the less your reader yet knows about the characters/plot, the simpler it will be to slip something in the reader will likely forget about until it becomes important later. If your reader mentions he has a sister working at [company] before [company] ever becomes important, it is more likely for the reader to take the fact and move on than if they just learned last chapter that [company] is doing something strange. If the sister is brought up following some suspicion being thrown on the company she works for, the reader is more likely to assume the sister is playing a larger role than we yet know about.
• Spread foreshadowing out. Similar to utilizing dropping clues long before the reader has a reason to pay attention to them, it’s smart to not pile too many clues right on top of each other. If your readers just learned one piece to the puzzle, give it a little time before you give them another. This is especially true if the pieces don’t necessarily seem to connect. The farther apart you keep them, the less likely readers are to make the jump that X and Y must be related (or else why would they both be right here?)
• Keep your characters from trying to purposefully mislead the reader (repeatedly). While it’s perfectly fine to have your character make an assumption that turns out to be wrong, don’t try to “trick” the reader by bringing up the wrong assumption repeatedly or you can quickly find yourself in a “The lady doth protest too much, methinks” situation. The more you bring up how obviously this means that, the more time the reader has to focus on that plot point and realize there must be more than meets the eye.
• Determine how common your “twist” is. A twist doesn’t always need to be unique. There is a saying that there are no new plots, and in a way that is true. You can write something that is a fresh idea, but that doesn’t mean that there aren’t any tropes in it. And the more well known a trope is (especially in your genre) the more likely it will be that readers will be able to figure out the “twist.” For example, if it turns out that the “big bad” is a relative of your protagonist, that twist is well enough known that you likely will be able to get away with just a few clues before people start catching on (because they’ve likely seen Star Wars and a number of other stories with that same twist). There is nothing wrong with using the trope all the same, just keep in mind what readers might be expecting when choosing how much to foreshadowing. Also keep in mind, if you intend to subvert a trope, you can also use these assumptions to your advantage. By letting the reader believe you’re following a common trope, it’s possible to sneak in other clues to what the real twist is while readers are distracted by what they believe will be the twist.
• Look for “throw away” lines. Especially if your twist is on the more common side, less is often more when it comes to foreshadowing. Readers are trained to expect that everything they read is important–after all, to keep up pacing, authors don’t tend to write in scenes that don’t matter to the plot. Because of that, if you put something in past the early “the reader doesn’t know what to look for” stage of a story that has a lot of attention drawn to it, the reader is likely to assume it is very important for some reason and take note. Look for ways to work in clues that are buried under other more obviously important information or in phrases that are nearly clichés. For example if someone says “what planet are you from?” when the twist is the character is an alien, the reader is likely to pass by the familiar saying less critically than something that sticks out as purposefully planted there (added bonus, the saying is also so easy to breeze over if you aren’t already thinking “aliens” that readers who have figured the twist out already will feel smart having caught it).

As with everything else, what exactly works for your story will be different from project to project. What is too much foreshadowing in one novel will be too little in another. When in doubt, look for beta readers who will be able to tell you if they figured your twist out too early or felt too blindsided at the end to have it be enjoyable. And then just keep on working at it.