Building conflict, internal and external and keeping what your protagonist desires just out of reach, is the key to establishing the rising tension that readers are expecting, while injecting the unexpected.
I remember writing a scene in my latest novel, Deep Deceit, where tension was building between two characters, conflict was palpable and as I wrote it I still didn't really know where it was going but I could feel the anxiety building in myself! When the scene climaxed, even I was shocked at what happened. The result of that scene then continued to escalate the overall tension leading to the ultimate climax of the story.
No matter what type of structure you follow, whether you're a plotter or pantser (I fall somewhere in the middle), no matter how many chapters and scenes, all stories have:
An introduction to your characters A situation, brought in early on, that creates a central conflict for the main characterAn escalation of tens…