Another way to increase tension is to foreshadow coming events. This is more subtle but when used effectively can raise the hairs on the back of the reader’s neck.
Early in your book, foreshadow a scene that might not take place until the end. For instance:
Warnings: In first chapter, a child is playing near a dangerous well and is warned to stay away. Later, he falls in and must be rescued.
A father says, “That John Doe. He’s no good.”
Dangerous weapons: The antagonist in an early chapter is described playing with a knife. He uses it later to kill his victim.
An arms collectors shows off his antique collection. Later, one is missing.
Weather: A storm threatens in the early scenes and then hits the characters in the latter chapters.
Drought worsens as book moves into final scenes.
Subtle dialogue: Today was going to be the best day of her life.
Mysterious events: A chair out of place, the smell of smoke in an abandoned house