Clear and frequent communication with graduate students throughout their program is the key to building the trust and mutual respect that form the foundation of the most effective supervisory relationships.
Meetings with graduate students are also good opportunities to discuss any particular needs or deficiencies of the student, as well as their career aspirations. You can then explore with them useful avenues for their development.
The best mentors lead in part by example, and including students as appropriate in your professional life is an effective way to share your knowledge and experience. Openness about the challenges you face or the excitement you feel, and involvement of students in broader dialogues with your peers all help assimilate students into the professional culture and broaden their learning experience.