Our study explores teaching practices that aim to promote students' learning to define an analytical object. A Calculus II instructor conducted a teaching experiment (TE) in which 11 students reinvented a formal definition of a limit over five class periods with the instructor's guidance. During the TE, the instructor's teaching practices were based on what principles of definitions from the literature inform about defining discourse. Our analysis of the instructor's teaching practices and students' follow-up work revealed several teaching practices that seem to promote development of students' narratives towards a formal definition of an analytical object: Providing testing methods to check if students' narratives can be considered as a completion of the defining task, asking students to place components of their definitions on graphs with related quantities, and asking them to reflect their illustration of the definition in their written definition. [For the complete proceedings, see ED658295.]