This article describes a one semester Professional Development for Teaching (PDT) seminar designed for mathematics Graduate Teaching Assistants (GTAs) that focuses on the implementation of active-learning techniques. The PDT seminar models active-learning strategies so GTAs have experiences to draw on when teaching undergraduate classes. A week-by-week outline of a PDT seminar schedule and an appendix of active-learning strategies are provided. Techniques for creating buy-in for active learning among the GTAs and debriefing about student evaluations of teaching are addressed.