Considering the importance of subject retrieval for scientific visibility, and the need to guide authors in self-archiving their papers in institutional repositories of university libraries, this study observed the patterns and strategies used by authors while indexing for keyword assignment. The study examined four categories of analysis: criteria for keyword assignment; use of controlled vocabulary for keyword assignment; understanding of the importance of keywords; and ordering criteria and function of assigned keywords. The study found that, while assigning keywords, authors: consider fundamental concepts for representing significant content of the text; act as domain expert indexers; and are unaware that keyword assignment is an indexing process that requires controlled vocabularies. The research suggests that institutional repositories implement a hybrid information representation and retrieval system to allow for both the representation of more specific subjects of knowledge domains, as well as controlled vocabulary indexing terms.