How to write a good prompt, step by step
Write four parts in this order: context (who you are and who it is for), task (what exactly it has to produce), criteria (what makes it right) and format (length, structure and how it ends). With those four the first answer is already usable; with one missing, the type of failure tells you which one it was.
The four parts
How you can tell which one is missing
- Missing context and the answer reads as if it were for anyone.
- Missing task and you get theory instead of a finished piece of work.
- Missing criteria and the text sounds fine yet still does not sound like you.
- Missing format and you have to reorganise the result before you can use it.
That diagnosis is the practical part: rather than rewriting the whole request, you look at the kind of failure you got and add the part that was missing.
One prompt, built end to end
"I am a dietitian running a small practice. [context] Write the reply to a patient cancelling tomorrow’s appointment for the third time. [task] I do not want to sound annoyed or apologetic, and it has to be clear that the next cancellation with under 24 hours’ notice will be charged. [criteria] Friendly, five lines maximum, no exclamation marks, and end with a question that is easy to answer. [format]"
Notice what is not there: no "please", no "act as an expert communicator", no adjectives like "professional" or "warm". Adjectives are stretchy and the AI fills them with the average. "No exclamation marks" and "five lines maximum" can be met or missed, which is exactly why they show up in the result.
What to do with one that works
Keep it. The difference between getting it right once and getting it right every time is having the prompt written down with gaps in it: swap the name, the date and the reason, and go. Within three months you will have ten or twelve covering most of what you repeat, and that beats any "100 prompts" list off the internet, because yours have your context inside them.
A good prompt is not memorised: it is assembled from four parts and kept for next time.