Students are a key element in the educational process and, consequently, their opinions, perceptions and feedbacks are an important input for the assessment and improvement of different aspects of the process. In this research, a questionnaire was designed and administered at the beginning of an undergraduate course to gather the opinion of the students about the importance of several aspects to determine the quality of teaching. The analysis of the survey data show which are the aspects that students consider more relevant for determining the teaching quality of a course, along with those that are not considered so important. Moreover, differences of students' opinions on the different aspects in terms of three characteristics were observed: gender, expected grade of the course and prior interest in the subject. With this information lecturers can do a better programming of the different aspects of the course and prepare the subjects more effectively, which is likely to positively impact student satisfaction which, in turn, has been related to an improvement in students' performance.