What is the best way to organize files? | Build Your Second Brain Series (6/10)

A simple “Johnny Decimal” (JD) system—organizing files into 10 numbered areas and then numbering subcategories—aims to make digital documents instantly findable and keep teams aligned. Instead of relying on memory or random folder naming, the method uses sequential numbering so the most frequently used categories naturally appear first, reducing the time spent hunting for the right place to store or retrieve a file.

The JD system starts by dividing everything into 10 main areas. In a company setting, those areas might be finance, marketing, sales, or administration; for an individual, the areas can be personal, academic, tools, and so on. Each main area is then broken into multiple categories, with a sequential number assigned to each category. The result is a unique numeric “address” for every folder. That structure brings three practical benefits: categories sort automatically, folder locations become easier to remember through “hand memory,” and file queries speed up because users can jump directly to a folder by typing its number. The system also emphasizes a key operational rule: nothing should be more than two clicks away.

Crucially, the method isn’t limited to one storage location. The same folder logic should be replicated across every part of a “second brain” workflow—explicitly including Google Drive, Zotero, and Obsidian. When the numbering scheme stays consistent across applications, adding a file to the correct place becomes less of a decision and more of a routine. That consistency also helps teams: a shared structure reduces the need to repeatedly explain where information lives.

The transcript then illustrates the approach with a Google Drive layout tailored to a PhD student. The drive is divided into 10 main areas, with smaller numbers reserved for the areas the user works on most. A “readme” file is placed in the top-level structure to clarify what each area contains—especially useful when collaborating. The example categories include “Home” for personal material (with a practical note about what could be donated if needed), “Academic” for coursework and related subjects, and “Tools” for microcontroller work, programming, simulation software, and daily research tools.

Other areas include “General,” which holds everything outside academic studies such as books (non-fiction and fiction), personal knowledge management, finance, investment, and productivity. The most important area, “Content,” is reserved for internet-facing outputs: YouTube videos, blog content, books in progress, future publishing plans, courses, and social media posts. The takeaway is straightforward: there isn’t a universal “best” organization method—what matters is adopting a structure like JD that fits how the user (or team) actually works, and then applying it consistently.