When to use categories
Categories (along with other features like cross-references, lists, and infoboxes) help readers find information, even if they don't know that it exists or what it's called.
Every page in the article should belong to at least one category. The categories to be included, which serve as classifications, should be the significant (useful) topics to which the subject of the article most closely belongs to as a member, and where readers are most likely to look if they can't remember the name of the thing they are trying to look up. For example:
Article: Elmsley Count Useful category: Cards Not as useful: Category: Counts that start with E
Questions to ask to determine whether it is appropriate to add an article to a category:
- If the category does not already exist, is it possible to write a few paragraphs or more on the subject of the category, explaining it?
- If you go to the article from the category, will it be obvious why the article was put in the category?
- Is the category subject prominently discussed in the article?
If the answer to any of these questions is no, then the category is probably inappropriate. Note that it is always appropriate to add articles to categories that fit into well established taxonomies. For example, every article about a Magician's book is categorized in some category, which is in turn categorized in Category:Books by authors.