Problems in mentorship most offer occur because of misunderstanding about expectations faculty and students have of one another. To avoid this, you need to clarify your respective roles and responsibilities. You may want to discuss:
Goals: Ask your students to develop and share with you a work plan that includes short-term and long-term goals as well as the timeframe for reaching those goals.
Meetings: Inform students about how frequently you will be able to meet with them.
Feedback: Discuss how often you will give them feedback about their general progress.
Drafts: Discuss your expectations of what first drafts should look like before they are submitted to you.
Publishing and presenting: For graduate students, discuss your philosophy and expectations about co-authorship and your ability to help your students prepare work for submission to journals and conferences.
Intellectual property: Clarify in advance who owns the data that is being collected; follow the university intellectual property guidelines.
Recommendations letters: Let student know how much time you need to write letters on their behalf.