We report on an analysis of ‘decision points’ that occurred during first year undergraduate calculus lectures. We analysed 135 accounts written by three lecturers concerning their own teaching; these accounts were written during a professional development project on employing the Discipline of Noticing (Mason, 2002). We classified the decision points in these accounts into eight categories. Furthermore, the triggers of these moments were identified and classified into seven categories; of these, the majority (58.2%) arose as a result of the lecturer monitoring either her own practice or the students’ engagement.