Wikipedia: The Missing Manual

Building Out Categories

Suppose you’ve found a good category for an article you’re working on, and when you get to the category page, you’re surprised that there aren’t many more articles listed there. Consider your surprise an opportunity to improve Wikipedia. You can take up the challenge to make the category page a much better place for readers to go.

WikiProject members do this type of work all the time. They look for articles encompassed by their project, and then add WikiProject templates to article talk pages and categories to articles. You don’t have to be a member of a WikiProject, however—just someone who realizes how useful categories are to both readers and editors.

There are significant advantages to working from a category page outward, looking for articles to add. Use existing articles to get clues to similar topics, both by reading the article text and following internal and external links in the articles. If you’re fairly knowledgeable on the topic of a category, so much the better; you’ve probably got a lot of good ideas about articles to look for.