Although modern search systems require minimal skill for meeting simple information needs, most systems provide weak support for gaining advanced skill; hence, the goal of designing systems that guide searchers in developing expertise. Essential to developing such systems are a description of expert search behavior and an understanding of how it may be acquired. The present study contributes a detailed analysis of the query behavior of 10 students as they completed assigned exercises during a semester‐long course on expert search. Detailed query logs were coded for three dimensions of query expression: the information structure searched, the type of query term used, and intent of the query with respect to specificity. Patterns of query formulation were found to evidence a progression of instruction, suggesting that the students gained knowledge of fundamental system‐independent constructs that underlie expert search, and that domain‐independent search expertise may be defined as the ability to use these constructs. Implications for system design are addressed.