At Oregon State University, the introductory calculus-based physics sequence utilizes social engagement as a learning tool. The reformed curriculum is modeled after the Interactive Science Learning Environment from Rutgers University, and makes use of Peer Instruction as a pedagogical tool to facilitate interactions. Over the past two years we have utilized a number of techniques to understand how to facilitate activities that promote productive discussion within the large lecture classroom. We specifically seek student discussion that goes beyond agreement on conceptual questions, encouraging deeper discussions such as what assumptions are appropriate, or how different assumptions would change the chosen answer to a given question. We have quantitative analysis of engagement based on video data, qualitative analysis of dialogue from audio data, and classroom observations by an external researcher. In this paper we share a subset of what we have learned about how to engage students in deep-level discussions during lecture.