Each card holds a single idea
An atomic concept that can be understood by itself. This makes each card useful in more than one context, increasing the surface area for expansion.
Use specific and contextual tags and avoid categories
’Finance’ or ‘Holiday’ are not good tags in Zettelkasten. In what context would you want to find information about ‘Finance’? It is too broad. A better version would be ‘Money Saving Tips’ or ‘Places I Want to Visit in Africa’. When tagging the notes, do not automatically link them to the most obvious and commonly used tags. Think hard about in what contexts this note may be helpful. This deliberate practice of linking is the essence of Zettelkasten. The existing keywords are warnings. They are not cues. In short, do not tag notes with subjects or keywords like in an academic paper. It makes note-taking a lazy activity.
Build the links among cards through references
The practice of deliberately building links helps connect ideas. Building links from the bottom up means constantly updating links as you gain new knowledge and insights. When implementing Zettelkasten digitally, a Related Notes section simulates the effect of putting related notes physically together. The idea is that when researching a note, closely related topics may spark insights.