Keep your taxonomies organized! This means keep your categories, tags and any other custom fields organized. Follow the taxonomies outlined in your sitemap. Also try to limit the categories or tags applied to a post - this will keep your content relevant to the viewer.
To edit or add a taxonomies go to: Posts > Categories (tags, or custom taxonomy title)
Click ‘edit’ on the title you would like to edit. Edit the ‘Name’ or ‘Parent’. If you would like to change the ‘Slug’, note that the old url will no longer work. You should create a redirect or avoid editing the ‘Slug’.