In this paper, we explain a user centered approach to collaborative information retrieval where the focus is not only on the system but on the users' interactions in solving an information problem. Our approach consists in facilitating knowledge sharing among users during information retrieval process through annotation and interpersonal communication. We created an environment for users to share their knowledge synchronously and asynchronously during information problem definition and clarification; while choosing information system to be used for search; during formulation and reformulation of queries to express their information problem based on the information system chosen; and during the evaluation of information relevancy to the resolution of their information problem.