The suspense fiction is much different than mystery. Although, they both deal with a crisis hook to keep the reader entertained and the story going, the narrative approach is different. In a suspense you must reveal details to your readers, because a suspense creates drama before the crisis occurs, whereas a mystery begins after the crisis. You must let your readers know everything that is at stake in the beginning, thus creating tension by introducing a strong hero and villain. Then there must be some sort of event that is absolutely devastating to the protagonist's world. As a suspense writer you must set up a trap for the reader, giving them a sense of hopelessness so that all they can do is turn another page.
Many writers think villains need to be translucent, but in a suspense fiction they need to be crystal clear. They need to be intelligent and have great motivation, wants and needs. Give the reader the exact reasons this person wants to inflict torture or a sense of horror on others. Readers need to be afraid of the villain. Fear is what builds suspense in writing suspense. The villain must also be a worthy opponent for the hero. In writing a believable villain, the hero must be equally believable and well written. Readers must be able to identify and care about the hero. There must be a way for readers to connect with the hero and root for them to overcome the villain. Suspense writing is about starting with the heat at 90 degrees and then raising the stakes from there to make it even hotter.
There are many ways to create problems and conflict to keep readers in suspense. Using time as a conflict keeps the protagonist working against the clock, and the clock working for the villain. In modern suspense fiction, the hero has 24 hours to complete his task or save the day. Every minute you shortchange a hero is another degree of heat for the reader. The hero should be stretched to a breaking point, bend but never buckle, meaning there is only one person left feeling helpless in the story: the reader. By giving the protagonist more hurdles than he can handle you are creating a sense of suspense and keeping the reader turning pages.
Nothing should run according to plan for your characters. A protagonist should never be able to rely on anything. Most importantly anything the hero does should have a price attached. Sir Issac Newton's theory of physics, is applicable to suspense fiction in that, for every action there is an equal reaction. The hero must have to improvise just because of the mere existence of the villain in the hero's world. This also means they don't have to be the only conflict in one another's worlds. Outside forces are also a great way to be unpredictable. When writing unpredictably, be sure to keep the storyline fluid. The reader might be able to guess what the end game is, but not how they are going to get there.