Librarians who teach one-shot library instruction classes (one-time, one- to three-hour classes to students who are assumed to be novice researchers) are often torn between two pedagogic approaches: a "critical mass" pedagogy emphasizing a minimum amount of databases that must be introduced with little time for student searching, and a "use-oriented" pedagogy emphasizing the introduction of one or two databases, with the instructor providing adequate time for the student to hone their search skills through in class work time that provides for interaction with the librarian. Drawing from the learning theory of Brian Cambourne, we compare the two pedagogic approaches and argue that a use-oriented approach is a better match to Cambourne's Conditions of Learning, but that without certain preparations of and expectations from the student, librarians will struggle with both approaches in these one-shot library instruction sessions. (Contains 1 note.)