The perception of being a prepared and thus competent instructor takes many, consistent small efforts and quite a bit of forethought. To be perceived as disorganized and thus an instructor of lower quality is more easily attained in the eyes of the students, because they have their bar set low to begin with for the most part. Consistent planning well before your given class time, beginning class on time, having your materials ready, not fumbling about with your slides or attendance sheets goes a long way to gaining the trust of your students.