A reference card that works

The best quick reference answers one recurring question at a glance.

The observation

A quick reference should answer one recurring question without requiring interpretation. Put the comparison or instruction first, then add source, date, and exceptions in smaller type.

A reference card that works is less a rule than a useful test: does the arrangement make the next encounter clearer?

In practice

Use tables only when the columns expose a real comparison. Keep units explicit, order entries by use rather than collection history, and remove decoration that competes with retrieval.

A closing note

A reference earns trust through provenance and revision. Mark when it was checked and make outdated material visibly obsolete rather than silently ambiguous.