As a teacher, I practiced cold calling in the classroom starting with my third quarter of teaching (Spring 2009-2010) and have continued it since then. Cold calling is a protocol used in classroom-style instruction settings (or other similar settings) where the instructor calls on individual students to answer questions posed by the instructor on a regular basis during lecture. The link discusses many issues related to the advantages, disadvantages, and implementation details of cold calling. My personal experience with cold calling has been largely positive. I give students the option of opting out of being cold called, and a few students have taken me up on the offer. As far as I recall, two students have requested to opt out of cold calling for the duration of the entire quarter that I taught them. There have also been other instances where students have requested to opt out of being cold called for a particular lecture because they were feeling unwell or having difficulty speaking.
The main trick I’ve faced with cold calling is how to combine making it a low-stakes and non-confrontational experience (in order to minimize stress) with being persistent in the face of students getting confused or stonewalling. I’ve found some types of phrases and word choices give me the subjective impression of working better at striking this balance. However, I don’t have a genuinely clear idea of how popular or unpopular a particular aspect of my cold calling is because students may hesitate to offer frank feedback.