In Ahrens’ book How to Take Smart Note, the author categorised notes into five types. I agree with most of it but wanted to tweak it to suit me better. After all, note-taking is a very personal thing.
Fleeting Notes
Your scrawls on serviettes, brown bags, or coffee shop receipts. They are random ideas you jolted down while reading, waiting, waiting in a queue, or talking with a friend. You write down your experiences, what you have done, how you achieved it, the light bulb moments, or the mere inferences you drew from your gut feelings.
Process them within a day or two while the memory is still fresh. You can bin these after you’ve turned them into permanent notes.
Permanent Notes
Notes that represent atomic ideas which can be understood in their own contexts. I occasionally create notes to connect related ideas when they are too big to fit into a single Zettel.
The title of the Zettel should be descriptive. The first sentence or paragraph should be the summary of the idea.
If combining two or multiple concepts sparks new insights, create a new note for the connection alongside the insights.
Literature Notes
Summarise the content of a book, publication or blog post and give the citation in the format of “on page X of Y, it says Z”. You can keep a separate bibliography slip-box with tools such as Zotero or org-ref.
Index Notes
Index notes are the entry points to your slip-box universe. Each index should link as few notes as possible (Luhmann links a maximum of three). Index notes are not table of contents containing links to everything in the slip-box. The key idea is to use the key links to discover more notes by traversing the network. If you use a digital Zettelkasten system, this type of note may not be necessary - back-links can be discovered by the software easily.
The fundamental principle is that Zettelkasten is not a categorisation or filing system. Do not design a top-down category system. Let the relationship form and emerge as you keep adding notes. If no insights or relationships are apparent among many orphan notes, it’s a sign that you are missing the linking step of Zettelkasten note-taking.
Project Notes
Notes that serve as ‘folders’ for specific projects. You can archive them or bin them once the projects are done. You draw ideas from your permanent notes, but you don’t change them for the projects - keep the modifications for the project-specific context inside the project notes.