I have tutored elementary, middle school, high school, and college-level students for many years now, and have been a TA for numerous courses in the Chemistry Department at UCLA. I believe that the three most important factors of a good tutoring session are communication, collaboration, and confidence.
At the most basic level, good communication is a necessary part of tutoring. As a tutor, I listen carefully in order to pinpoint the source of a student's confusion.
It is also necessary for a student to be an active participant in the problem-solving process. I try to collaborate with the student, guiding the student towards a solution.
At the end of a session, a successful tutor will have given the student the confidence needed to put new knowledge into practice. I believe that the best way to instill confidence is to first understand the student's problem areas well, and then carefully guide the student towards the solution. The "Aha!" moments that arise during this process create a fun learning environment while increasing a student's self-confidence to solve similar problems in the future.