How do I practice data classification?

The most direct way to practice data classification is through a focused exercise: Pick one domain where you currently sort things without written criteria — your email folders, your project labels, your bookmarks, your reading list. Write down the actual categories you use. Then, for each category, write a one-sentence definition that would let someone else sort items the same way you do. Where you can't write the definition, you've found an implicit category that needs to be made explicit.

Common pitfall: Creating explicit categories and then never revisiting them. The point of making categories explicit is not to freeze them — it's to make them visible so they can be evaluated and improved. If you define your categories once and treat them as permanent, you've just traded one kind of rigidity (implicit, invisible) for another (explicit, fossilized). Explicit categories need periodic review.

This practice connects to Phase 12 (Classification and Typing) — building it as a repeatable habit compounds over time.