In addition to selecting a metadata standard or schema, wherever possible you should use a controlled vocabulary. A controlled vocabulary provides a consistent way to describe data. Examples of controlled vocabularies include subject headings, thesauri, ontologies, and taxonomies. Using a controlled vocabulary will aid in searching and finding your data and will make your data more shareable with researchers in the same discipline.
For more information and lists of controlled vocabularies used in various disciplines, see the JISC (Joint Information Systems Committee, U.K.) website: