There are always exceptions, of course, but as a rule, never write a story solely for the sake of a twist. When you do that, it's usually obvious. Blatantly and painfully obvious. I've actually sat some out. I mean, I've gone ahead and read through some stories even after recognizing early on that there was going to be a twist at the end � and that the twist was going to be the main point of the entire story. And I could almost always predict what the twist was going to be. Some writers simply can't mask the clues. Some writers are too eager to show off how clever they think they are. And some writers just go ahead and point out their clues with flaming lances. The whole point of the twist is that no one is supposed to see it coming � not even your characters. Or maybe I should say, especially not your characters. There's some excitement in a reader knowing a twist before a character. A reader keeps reading to find out how the character will react when the twist comes into play. This works great in comedy. Happened a lot in Jeeves and Wooster. The audience is shown a twist in a situation or character, and you just know Bertie Wooster is going to stumble into a hilarious scene.
A twist is meant to be a surprise, and that doesn't mean that it has to come at the end. What if the twist you're saving for a big bang at the end fizzles out? There's little more disappointing than a story built up to an anti-climactic ending due to the author's belief that they have an awesome twist to present at the end of their story when they really don't. And if the characters, even, aren't surprised or don't care about the new situation they discover, so much the worse.
A twist in the middle can send your story in a new direction and refresh the action. It can change or alter the goal, possibly presenting more obstacles for your character(s) to work around and, therefore, creating heightened suspense. Having multiple twists isn't a bad thing, either, as long as it's relatively believable and doesn't send your story into unrecognizable chaos. It's ok to confuse your audience, but don't let them stay confused for too long. They may lose interest or think that you don't know what you're doing.
Some writers fall into a habit of writing twists. Not good. But, hey, reviewers liked it the first time!! I got so much praise, and that's why I write!!! For the praise!!!! So why can't I??? I'll tell you. If readers come to know you as a twist writer, your twists will be expected and, therefore, meaningless. Watch yourself. Most people prefer a well-writen story to the tiresome and predictable twist.
Bottom line, be careful. Don't let your twist completely govern your plot. Try not to give too much away, but at the same time, don't make things so vague that your readers can't follow the plot. Ask an honest friend to read your story and tell you if it's going well. Tell them beforehand that you want them to pay attention to whether they can see a twist coming, or if it's too vague or maybe that too much informaiton is given too soon or at one time. You can't always be your own judge of such things.
