Like a good magician, unfolding a mystery takes a little "sleight of hand." If you draw attention to what you are doing, then someone will inevitably peek behind the curtain. Rather, you must distract the audience to maintain your secrets. Make sure they see only what you wish them to.
Anything can be a distraction in a story: a character's actions, words, circumstances all can lead the attention in the desired direction while you perpetrate your trickery unobserved. But cheap gimmicks rarely yield the most satisfying results. The best mysteries are the ones where, once revealed, seem so obvious. You find yourself wondering why you didn't figure it out sooner.
There is a distinct advantage the author has: they know the secrets. And thus, they can weave a tapestry with many colored threads all going in different directions. Patterns form, but the entirety of the work is not seen until the end.
In the case of a series, secrets will be revealed along the way. In a shorter work, the reveal occurs a bit sooner. But with either, there comes that moment when the cloth is jerked away and the audience "oohs" and "aahs" over the results. At that time, the magician takes a well-deserved bow.