Mathematical modeling has taken on increasing curricular importance in the past decade due in no small measure to the Common Core State Standards in Mathematics (CCSSM) identifying modeling as one of the Standards for Mathematical Practice (SMP 4, CCSSI 2010, p. 7). Although researchers have worked on mathematical modeling (Lesh and Doerr 2003; Pollak 2003, 2012), much remains to be learned about modeling and how to teach students to use modeling appropriately, particularly at the secondary level. This article uses high school classroom episodes to address an aspect of modeling called "mathematizing," the process of translating a given situation into its mathematical model (Blum and Ferri 2009). These classroom episodes are used to illustrate and analyze: (1) the ways of thinking that help students' engagement with mathematizing; and (2) how teachers can support students in developing such ways of thinking.