Search various categories for stub articles. Stub articles belonging to a specific category with minimal content should be merged into a meta-article covering that subject matter.
Rather than delete old pages, redirects should be employed to reduce the chance of users making an article for the same subject. Furthermore, if the stub does have a chance to move beyond stub status, the article can be re-developed on its own merits as a category member.
Duplicate references should be identified by human or bot as a method of detecting merge-candidates, or overlooked category members. Furthermore, duplicate references that are required should be converted to a template that would appear uniformly on all category member pages.
Parent categories of significant volume should be reasonably sub categorised. Template:CatDiffuse explains this process.
Templates should be used to eliminate redundant content within category articles.