In stories, characters that a writer devotes the largest proportion of wordcount to are those that the reader will assume are most important to the plot.
For example, if a dead body is found and the writer spends ages telling us all about Crazy Joe, who lives next door, hated the dead person and spends inordinate amounts of time cleaning and sharpening his axe, then the reader is going to regard CJ as being the prime suspect.
As a writer, you can use these assumptions to your advantage. Say, for example, that the real killer is Sarah, who was bullied/jilted/abused by the dead person at some point in the dim and distant past.
By giving more storytime to Joe instead of Sarah, you effectively hide her behind all those words and give yourself the perfect opportunity to twist the end of the story.
Just be careful that you include Sarah in the story from the beginning, though. It isn’t fair to your readers to introduce her in the final scene. They are likely to feel cheated if you do that.
So there you go – misdirect your readers by sleight of hand. Get them looking at your left hand, while your other hand hides a rabbit behind their ear … or something like that.