On rainy writing days I tinker with the voice first, because an unreliable narrator lives or dies by the way they talk. I start by giving them a confident cadence and then quietly
sabotage it — small contradictions, odd gaps
in memory, and a habit of explaining away details. That rhythmic wavering is more effective than a single big lie; sprinkle tiny lies across scenes so the reader’s trust decays slowly.
I like to pair that technique with structure. Try an epistolary setup — diary entries, voice memos, or transcripts — and let the medium betray the narrator. A torn page, an interrupted recording, or an entry written in a shaky hand all imply breaks between what the narrator intends and what actually happened. Alternating chapters from another character or an objective log can make contradictions sting.
Finally, think about motive: why is your narrator unreliable? Are they protecting someone, protecting themselves, unknowingly deluded, or actively manipulating the reader? Layer sensory details that contradict their claims (a narrator says a room is bright but describes shadows) and let other characters react in ways that reveal the truth. When the reveal comes, it should feel earned rather than cheap — like the last piece of a puzzle snapping into place, and that payoff is what I live for when I read mysteries.