[LLM] How to Write Effective Prompts

Sat, 21 Feb 2026 20:40:00 +0900

Introduction

Writing effective prompts is essential for getting the most out of LLMs (Large Language Models). This article summarizes key principles and practical patterns of prompt engineering.

Core Principles of Good Prompts

1. Clarity

Avoid ambiguous expressions and be specific.

Bad Example:

Write good code

Good Example:

Implement a binary search tree in Python.
Include insert, search, and delete methods,
with time complexity of O(log n).

2. Provide Context

Give background information needed for the LLM to understand the task.

I'm a React beginner.
Explain the difference between useState and useEffect
with example code.

3. Role Playing

Set up responses from a specific expert’s perspective.

You are a senior backend developer with 10 years of experience.
Explain the pros and cons of microservices architecture.

4. Specify Output Format

Explicitly state the desired response format.

Summarize the following in a markdown table:
- Language features
- Pros and cons
- Use cases

Prompt Patterns

Chain of Thought

Guide step-by-step thinking for complex problems.

Let's think through this problem step by step:
1. First analyze the problem
2. Consider solutions
3. Write the final answer

Few-Shot Learning

Provide examples to teach the desired format.

Summarize in the following format:

Input: "The weather is nice today"
Output: Positive, Weather

Input: "The meeting was too long"
Output: Negative, Work

Input: "Started a new project"
Output: ?

Structured Prompts

Divide complex tasks into sections.

## Goal
Design a user authentication API

## Requirements
- Use JWT tokens
- Refresh token rotation
- Apply rate limiting

## Output
1. API endpoint specification
2. Sequence diagram
3. Security considerations

Common Mistakes

Mistake	Problem	Solution
Too long prompts	Key points get lost	Keep it concise
Ambiguous instructions	Unexpected results	Provide specific examples
Missing context	Inaccurate answers	Add background info
Unspecified format	Poor readability	Specify output format

Practical Checklist

Check before writing your prompt:

Is the goal clear?
Included necessary context?
Specified output format?
Stated constraints?
Would examples help?

Conclusion

Good prompts are clear, specific, and provide necessary context. Practice to improve your prompt writing skills.

References

Korean Version: 한국어 버전

Prompt-Engineering on Yarang's Tech Lair