If you give them some time to blow off steam they can then begin to hear what you have to say. Know your school's process as well as financial aid regulations. Never promise something you can't deliver. If you're researching a problem for a student, keep in touch even if you haven't found the answer yet. Keep your appointments and return phone calls as promised.
Students generally have very tight schedules.
Know about alternative types of financial resources. Also, know what student services are available on campus and refer your students. Often, students need assistance because of a personal problem or crisis. Be realistic and realize that you can't help everybody. Whether you do or not will be dictated by your department's policies and resources.