This chapter is as close as the Tag Library gets to a guide to tagging JATS documents using the Archiving Tag Set. It provides descriptions of common tagging practices and guidance for specific tagging issues. Essays discuss JATS structures and the design choices involved in tagging complex conceptual structures, for example, author affiliations and keywords, which involve numerous choices among elements and attributes. This information is intended to be useful for those learning JATS and those working with JATS documents. In some cases we describe "best practice"; in other situations there is no consensus on best practice and we describe several common practices.