Abstract: We surveyed university mathematics instructors across the United States about their planning practices to better understand the complexities involved in the work that goes into preparing for instruction at the university level. Research indicates that the quality of instructors’ lesson plans can be linked to the quality of their instruction (Akyuz et al., 2012). Instructors self-reported as either using inquiry-based practices, lecture-based practices, or an even mix of both. Instructors who indicated using both inquiry-based and lecture-based practices spend more time lesson planning but often feel less supported by the lesson plans they create. These instructors attempt to do practices that both the inquiry-based instructors do (i.e., spend time preparing for and accounting for student thinking) and lecture-based instructors do (i.e., ensuring a clear understanding of the mathematics for themselves). We posit that placing student thinking at the center of both instruction and planning provides a guiding principle that can be used to support student learning outcomes. The undergraduate mathematics education community lacks a cohesive framework that clearly defines and integrates terms such as eliciting, building on, and leveraging student thinking, reflecting the complex relationship between student thinking and instruction of undergraduate mathematics. Here we discuss implications for instructors and the undergraduate mathematics education community as well as the next iteration of this work.