Redundancy and repetition should be avoided. There should only be a single article (or section of an article) where a given topic is presented in full detail. Other pages should link to the page with the details instead of repeating them.
Only information that is directly relevant to the subject of a given article should be included in that article.
Article and category names should be as precise and at the same time as short as possible.
For characters, titles and ranks should not be included in the article title. For example, if a character is called "Adjutant Percy," the article should be named "Sharon Percy." Full names are preferred if possible.
An article should always be categorized by characteristics of the topic, not characteristics of the article. A character article that contains descriptions of bugs, for example, does not belong in Category:Bugs.
An article should never be left with a non-existent (red link) category on it. Either the category should be created (most easily by clicking on the red link), or else the link should be removed or changed to a category that does exist.
User pages should not be placed in content categories. They may be placed in certain categories that explicitly allow doing so, otherwise, they should remain uncategorized.