A lot of beginner advice makes first-person sound like you're just sticking a camera on the narrator's forehead, but that's missing the real texture of it. The biggest gap I see is between a narrator who's aware they're telling a story versus one who's just experiencing events in real-time. In something like 'The Name of the Wind', Kvothe is consciously constructing his tale for the Chronicler—he curates, he reflects, he withholds. The perspective is filtered through his older, wiser, and possibly unreliable self. Contrast that with a present-tense, stream-of-consciousness style where the prose stumbles and leaps with the character's immediate panic or joy, like in parts of 'The Hunger Games'. Katniss isn't 'telling' us anything; we're trapped in her moment-to-moment reactions. That choice fundamentally changes how close the reader feels and what kind of truth we have access to.
Another common perspective pitfall is forgetting the narrator's sensory and knowledge limits. If your first-person character is in a pitched battle, they won't give you a clean, omniscient play-by-play of every flanking maneuver. They'll hear screams, taste blood and dirt, see fragmented glimpses of movement. Their perspective is physically constrained. Similarly, their internal commentary should match their background. A medieval scribe will describe the world with different metaphors than a modern-day mechanic. That voice isn't just vocabulary; it's the entire framework through which they interpret events. I've read drafts where a kid from a small town suddenly starts analyzing social dynamics with the jargon of a sociology professor, and the perspective instantly shatters.
Then there's the tricky use of other characters. In first-person, every other person is a translation. We only get the narrator's interpretation of their tone, their expressions, their motives. This is where you can build incredible dramatic irony—the reader might pick up on something the narrator misses because of their biases. A classic example is Nick Carraway in 'The Great Gatsby', who paints Gatsby with such romantic tragedy, while his view of Tom is dripping with contempt. We're getting Gatsby filtered through Nick's own yearning and disillusionment, not an objective portrait. That's the power of the perspective; the story becomes as much about the narrator's psyche as the plot itself.