The Smooth Transition for Advancement to Graduate Education (STAGE) project was a three-year pilot project designed to mentor undergraduate students primarily from under-represented groups in the mathematical sciences. The STAGE pilot project focused on mentoring students as they transitioned from undergraduate education to either graduate school or a career in the STEM workforce. We discuss the various mentoring structures, the STAGE pilot utilized, and how those structures affected programmatic outcomes. In addition, we discuss challenges we faced in mentoring undergraduates and special considerations we made when mentoring students from under-represented groups.