A useful prompt library is not a collection of a thousand clever prompts. It is a small set of reusable instructions for your actual work.
Start with frequent tasks
Pick tasks such as meeting notes, email rewriting, competitor research, article outlines, social captions, translation, long-document summaries and project retrospectives.
Define what good output means
Each template should include role, goal, input, constraints, output format and evaluation criteria. The evaluation criteria matter most: avoid hype, cite sources, use a table, ask questions if information is missing.
Save failures too
Bad outputs teach you what constraints are missing. Record whether the result was too generic, too long, unsupported, off-brand or hard to use.
A reusable template
“You are [role]. I need [task]. Context: [background]. Use [input]. Output [format]. Constraints: [limits]. Quality bar: [criteria]. If information is missing, ask up to three questions first.”