Your commonplace book is a treasure trove of quotes, ideas, inspiration, and insights — but if it’s not organised, it can quickly turn into a chaotic dump of content. That’s where a key system comes in.
A good key helps you:
✅ Quickly categorise your entries
✅ Spot patterns over time
✅ Make it easier to reference, review, and reuse ideas
In this post, we’ll show you how to set up a simple key system using colours, symbols, and short codes (abbreviations).


🔑 What Is a Key?
In the context of a commonplace book, a key is your personal system for labelling and organising entries. It can include:
- Colour codes (using highlighters, pens, or stickers)
- Symbols (like â or 💡)
- Abbreviations or short codes (like PHL for philosophy or CRV for creativity)
You can combine all three, or just use one — whatever works for how your brain works.
🖠Step 1: Choose Your Categories
Start by identifying the main themes or categories of content you intend to collect. Examples:
- 📚 Literature
- 🎬 Media
- 🧠Philosophy
- 🌿 Garden / Nature
- 🧬 Science
- 💻 Technology
- ðŸ½ï¸ Food & Drink
- 🔨 Home Improvement
Try to keep it to 6–10 main categories so it doesn’t become overwhelming.
🎨 Step 2: Assign Colours
Now, assign each category a colour. You can use:
- Highlighters
- Coloured pens
- Washi tape
- Stickers
Highlight the margin, title, or use a dot or underline in that colour for each entry.

âœ´ï¸ Step 3: Use Symbols for Quick Reference
Add a symbol next to each entry to visually indicate what type it is.
Suggested Symbols:
- â Favorite
- 💡 Insight
- 📠Writing idea
- 🔠Review this later
- 🔠Worth exploring
- 🎯 Actionable
You can mark symbols in the corner of the page, next to the title, or in the margin. Over time, you’ll be able to scan quickly and spot what’s important.
🔤 Step 4: Use Abbreviated Keys
If you like indexing or want to cross-reference topics, use 2–3 letter codes. For example:
- PHL = Philosophy
- WRT = Writing
- CRV = Creativity
- QTE = Quote
- RFL = Reflection
- LIF = Life Advice
You can write the code in the margin or next to your page number in the index.
🗂 Step 5: Create a Master Key Page
At the front (or back) of your commonplace book, create a Key Page where you list:
- All categories
- Their assigned colours
- Symbols and what they mean
- Abbreviation codes
That way, you always have a reference if you forget or want to tweak things later.

🔄 Example Entry (Putting It All Together)
Page 17
Title: “On Courage†— Epictetus
Key: PHL 💡 ðŸ”
Highlight: Blue
“First say to yourself what you would be; and then do what you have to do.â€
Index Entry:
| Title | Page | Key |
|---|---|---|
| On Courage | 17 | PHL 💡 🔠|
Final Tips
- Keep it simple at first — don’t try to code everything. Let your system grow with you.
- Use consistent markings so you can trust the system later.
- Leave space to update your key page — your interests may evolve.
Your Commonplace Book = Your Brain on Paper
A key system isn’t about being fancy — it’s about making your ideas findable, usable, and reviewable.
Over time, your commonplace book becomes more than a notebook. It becomes a thinking tool — a personalised map of your intellectual and creative life.
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