Prompt Engineering FoundationsEveryday mistakes and good habits · Lesson 15 of 16

Ten everyday prompting mistakes (and fixes)

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Ten everyday prompting mistakes (and fixes)

12 chapters · about 8 min · captions · full transcript

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Chapters

Mistake 1: the one-line prompt

Symptom: generic, bland results. Fix: add context, audience and format. Even two extra sentences transform most answers.

Mistake 2: assuming the AI knows your world

Symptom: the AI refers to the wrong product, invents company details or uses the wrong currency. Fix: state the essentials: who you are, where you are, who the audience is. "We are a UK-based charity; use British English and pounds."

Mistake 3: trusting facts without checking

Symptom: a statistic, quote, legal rule or source turns out to be wrong or invented. Fix: treat factual claims as leads to verify. Ask "Which parts of this are you less certain about?" and check key facts in reliable sources. Be especially careful with health, legal, financial and news topics.

Mistake 4: asking for everything at once

Symptom: half the requests are ignored or done badly. Fix: one task per message, or clearly numbered requests. Break big jobs into steps: outline, then draft, then edit.

Mistake 5: vague feedback

Symptom: "Make it better" produces random changes. Fix: say what is wrong and why: "Too formal for Instagram; my followers are students."

Mistake 6: never starting fresh

Symptom: a long, confused conversation where the AI mixes old and new instructions. Fix: start a new chat with a clear, improved prompt that includes what you have learned.

Mistake 7: not saying what to do when information is missing

Symptom: invented deadlines, prices or names that fill gaps. Fix: "If you don't know, write 'unknown'" or "Ask me instead of guessing."

Mistake 8: pasting private information carelessly

Symptom: customer data, passwords, confidential plans or someone else's personal details go into a tool without thought. Fix: remove or replace personal details ("Customer A"), never paste passwords, follow your workplace's AI policy, and check the tool's data settings.

Mistake 9: copy-paste without reading

Symptom: publishing text with errors, odd phrasing, placeholders like "[Your Name]" or claims you cannot support. Fix: read everything before you send or publish. You are the editor and you are responsible for the final result.

Mistake 10: giving up too early

Symptom: "AI isn't useful for my job" after one disappointing try. Fix: try the T-CAFE structure, an example, and two rounds of feedback before judging. Many tasks that fail on the first attempt succeed on the third.

A before-and-after example

Before:

write a product description

After (fixing mistakes 1, 2, 7 and 9):

Write a 60-word product description for our online shop (we're based in
Dubai; prices in AED). Product: handmade oud-scented soy candle, 200g,
burn time about 40 hours (from our supplier's spec). Audience: gift
buyers aged 25-45. Tone: elegant, not over the top. Don't add any claims
about health benefits. If you need details I haven't given, list them
as questions at the end instead of guessing.

Then the human step: read it, check the burn time matches the label, and remove anything you cannot stand behind.

Spotting a weak answer

Signs you should push back or verify:

  • It is very general and could apply to anyone.
  • It includes specific-looking numbers you did not provide.
  • It cites sources you cannot find.
  • It avoids your actual question.
  • It sounds confident about something that changes often (prices, laws, schedules).

The habit that fixes most problems

Before sending any prompt, ask: "If I gave this to a smart new colleague, would they have what they need?" If not, add what is missing. This single habit fixes the majority of everyday prompting problems.

Make it stick

Pick the two mistakes you recognise most in yourself and write their fixes on a sticky note or at the top of your prompt toolkit. For the next week, check each prompt against those two fixes before sending. Small, repeated habits improve your results far more than reading long lists of tips once.

Three newer mistakes to add to the list

As assistants gained new features, new mistakes appeared.

Mistake 11: using the wrong mode. Asking a quick-answer mode to solve a complex multi-step problem, or waiting two minutes for a thinking mode to rewrite a one-line caption. Fix: match the mode to the job. Quick mode for drafting and rewriting; thinking mode for multi-step reasoning, calculations and plans; web search or deep research for current facts.

Mistake 12: trusting an uploaded file blindly. You upload a 60-page PDF and assume the assistant read every page carefully. Long or scanned documents, tables and images inside PDFs can be partly missed. Fix: ask for page references ("quote the passage and give the page number") and check the most important answers against the document.

Mistake 13: letting memory or old instructions steer you wrong. Custom instructions, projects or memory from months ago ("always write in a formal tone") silently shape today's answers. Fix: review your saved instructions and memory every few months, and remove anything that no longer applies.

Hands-on: the prompt doctor

Paste one of your weaker prompts into the assistant with this message:

Act as a prompt coach. Here is a prompt I used and the answer I got.
1. Diagnose which of these problems it has: missing context, vague
   words, no format, no audience, too many tasks, no instruction for
   missing information.
2. Rewrite the prompt to fix them.
3. Tell me which one change will make the biggest difference.

PROMPT:
---
[paste your prompt]
---
ANSWER I GOT:
---
[paste a short excerpt]
---

Compare the rewritten prompt with your own diagnosis. Over time you will spot the problems before the coach does.

Measure your mistakes, then fix one

For one week, tag each disappointing answer with the mistake number that caused it. Most people find one or two numbers dominate. Fix those first; they are your personal highest-return habits.

Key takeaways

  • Most poor results come from one-line prompts, missing context and vague feedback.
  • Treat factual claims as leads to verify, especially numbers, sources, and health, legal or financial topics.
  • Tell the AI what to do when information is missing, and never paste private data carelessly.
  • Read everything before using it, and don't give up after one attempt.

Check your understanding

Quick questions to lock in the lesson. They don’t count towards your certificate.

  1. An AI-written post includes a statistic you never provided. What should you do?
  2. Which instruction prevents the AI from guessing missing details?
  3. Which is the safest way to include a customer complaint in a prompt?

Put it into practice

Review your last five AI conversations. Which of the ten mistakes did you make most? Rewrite one prompt to fix it.

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