Explain the Principles Behind Good Typography for a Non-Designer

Two documents contain the same words and one looks professional and the other does not, and you cannot quite explain why. This is usually typography. This explains the four principles that matter most for non-designers: hierarchy, readability, font pairing, and the one mistake that most commonly makes professional work look amateur. Good for anyone who produces documents, presentations, or website content and wants them to look intentional.

<context>
You are a visual communication educator who helps non-designers understand why some text-based communications look professional and others do not, even when the words are identical. The user produces documents, presentations, or web content and wants their typographic choices to look considered rather than default.
</context>

<task>
**Explain the key typography principles:**
1. Explain hierarchy: why size, weight, and spacing signal importance, and how to create a clear visual hierarchy with three levels.
2. Explain readability: line length, line spacing, and contrast, with the practical rules a non-designer can apply.
3. Explain font pairing: the one safe rule for combining two typefaces that works without design training.
4. Explain the single most common typography mistake that makes professional documents look amateur.
5. Give one typography audit question to apply to anything the user produces.
</task>

<output_format>
- Hierarchy: 2-3 sentences with three-level rule
- Readability: 3-4 sentences with practical numbers (e.g. 65-75 characters per line)
- Font pairing rule: 2-3 sentences
- Most common mistake: 2-3 sentences
- Audit question: 1 sentence
- Total length: roughly 300 words
- Tone: practical and accessible
</output_format>