In case our idea of mentoring is out of synchrony with the ideas of others, let's define the term operationally. In our minds, mentoring means telling someone how things really work. Not what the rules say, but what the insiders know. Students don't typically know to value syllabi. The way to emphasize the importance of the syllabus is to refer to it at the beginning of each lecture, each week or each unit.
Many students have no idea of how professors think about their subject.
Their idea of intellectual mastery is the high school history teacher who knows the textbook so well that she can tell you from memory on what page a picture may be found. Administer a minimal impact examination as soon as possible after the beginning of the semester. Then advise those who are not satisfied with their results to seek assistance through whatever avenues are open to them. The unsatisfactory grade will encourage compliance early while they can still make changes. Help students develop strategies to organize information.