You read space opera for years, dozens of books, and then one afternoon you realize maybe five or six ideas from those books actually rewired how you think about writing fiction. The rest was atmosphere. These are the ones that stuck.
The Best Space Operas Happen at the Border, Where Two Civilizations Can't Understand Each Other
Iain M. Banks built the Culture, a post-scarcity utopia governed by hyper-intelligent AIs called Minds, where nobody wants for anything and death is optional. And then he did something odd with it. He refused to set his stories there.
Almost every Culture novel takes place at the edges, in the messy friction between the Culture and civilizations that don't share its assumptions. Consider Phlebas follows a man fighting against the Culture. Use of Weapons centers on a mercenary the Culture hires precisely because he'll do things they won't. Banks understood that a paradise is boring until it bumps into someone who thinks paradise looks different.
This maps onto something diplomats talk about constantly. The most dangerous moments in international relations aren't when two countries disagree on specific policies. They're when two countries disagree on what counts as a reasonable way to resolve disagreements in the first place. The meta-conflict. Banks wrote science fiction about that gap, and it gave him an inexhaustible engine for stories, because the Culture kept encountering civilizations that operated on entirely different moral operating systems. If you're building a space opera, you don't need more planets. You need at least two worldviews that can't be reconciled without something breaking.
A Pronoun Choice Can Do More Worldbuilding Than a Hundred Pages of Lore
Ann Leckie's Ancillary Justice uses "she" for every character regardless of gender. The protagonist, Breq, comes from the Radch, an empire where gender distinctions don't register socially the way they do for us. Leckie could have explained this in a paragraph of exposition. Instead she embedded it in the grammar, and readers spent the entire book doing involuntary double-takes every time a character was described.
That one decision won the Hugo, the Nebula, and the Arthur C. Clarke Award in the same year. I think the reason it worked so well is that it made the reader's own assumptions visible. You'd catch yourself trying to figure out a character's "real" gender, and then you'd realize the Radch wouldn't even understand the question. The worldbuilding happened inside the reader's head, which is where the most durable kind of worldbuilding always happens. It cost Leckie zero words of exposition. One pronoun rule. That's it.
Your Biggest Character Might Not Be a Person
Gareth L. Powell's Embers of War has a sentient warship named Trouble Dog who volunteered for a rescue service as penance for participating in a massacre. Powell gives the ship a full interior life, guilt and longing and the slow recalibration of identity that comes from trying to become something other than what you were built to be. Trouble Dog isn't a vehicle. She's the emotional center of the book.
Leckie did something similar. The protagonist of Ancillary Justice, Breq, is a fragment of a destroyed starship's AI, forced into a single human body after spending centuries distributed across thousands of bodies simultaneously. The grief of that loss, going from a chorus to a solo, drives everything she does.
I'm honestly not sure why this works as well as it does. Maybe it's because a ship that feels remorse is inherently more interesting than a human who feels remorse, since we have to wonder whether the remorse is "real" or programmed, and that question turns out to be unanswerable in a way that keeps pulling you forward. Whatever the reason, it's a technique worth studying. If your setting includes AIs or sentient machines, consider giving them the emotional arc you'd normally reserve for your human lead.
Structure Can Be a Space Opera Technique in Itself
Banks' Use of Weapons is built on a structural conceit that would seem gimmicky if it weren't executed so precisely. One narrative thread moves forward in time. Another moves backward. They converge on a single revelation that completely reframes everything you've read. The forward thread shows you who the protagonist is becoming. The backward thread shows you what he's running from. When they meet, the collision is sickening.
Most space opera writing techniques advice focuses on worldbuilding and scale. Banks reminds you that how you tell the story is a choice with as much weight as what happens in it. A linear retelling of Use of Weapons would be a good book. The structure Banks chose made it a book people still argue about decades later.