Overgeneralizing commonly accepted strategies, using imprecise vocabulary, and relying on tips and tricks that do not promote conceptual mathematical understanding can lead to misunderstanding later in students' math careers. In this article, the authors present thirteen pervasive mathematics rules that "expire." With the implementation of the Common Core State Standards for Mathematical Practice, the authors conclude that now is an ideal time to highlight common instructional practices that teachers can tweak to better prepare students and allow them to have smoother transitions from grade to grade. The purpose of this article is to outline common rules and vocabulary that teachers share and elementary school students tend to overgeneralize--tips and tricks that do not promote conceptual understanding, rules that "expire" later in students' mathematics careers, or vocabulary that is not precise.