After a year of writing prompts daily, here is the uncomfortable truth: almost every trick that survived is something a good editor would tell you about writing a brief for a junior colleague.
Say who it is for and what done looks like
"Write about our product" fails for a human intern and it fails for a model. "Write 3 short options for a subject line for busy IT managers; under 8 words each; no exclamation marks" works for both. Specificity is not a hack, it is communication.
Show one example
One worked example in the prompt outperforms three paragraphs of description. This is the single highest-leverage habit we know.
Let it say "I do not know"
Adding "if you are not sure, say so and list what you would need to check" cut our hallucinated citations dramatically. Models bluff when the prompt implies bluffing is expected.
Stop collecting magic words
"Take a deep breath", "you are a world-class expert" — these move benchmarks by decimals on specific models and mostly add noise. Clear task, clear audience, clear format, one example. That is 90% of it.