This paper identifies salient practices of faculty mentors of undergraduate research (UR) as indicated in the extensive literature of the past two decades on UR. The well-established benefits for students involved in UR are dependent, first and foremost, on high-quality mentoring. Mentorship is a defining feature of UR. As more and different types of colleges and universities strive to meet student demand for authentic scholarly experiences, it is imperative to identify what effective UR mentors do in order to ensure student engagement, quality enhancement, retention, and degree-completion. We offer an original analysis of the literature on UR mentoring in which we identify 10 significant "lessons learned," or evidence-based practices of effective UR mentors that apply broadly across disciplines, students, institutions, and mentoring approaches.