The traditional pattern of classroom experience at the college level brings the professor and a group of 20 to 30 students together for a 45-to-50-minute class session two or three times a week. The most common mode of instruction is the lecture. When lectures are the principal method of instruction in larger classes, regular periods may be set aside for small group discussions under the leadership of an assistant instructor. In cases where a small class size encourages in formality, lectures may be combined with discussion sessions based on assigned readings, required textbooks, and other outside materials. Accurate, legible notes are invaluable aids to the student who is enrolled in a lecture course. Notes should be taken during lectures, and when the student is reading the texts prior to each session of the course. The key to good note-taking is to be able to listen a lot and to write only as much as is needed to re- cord the essence of a point or idea presented by the lecturer. Thus, students should endeavor to identify only the main points and ideas being presented and to mite them down in outline form. They should also strive to take good notes the first time and not play to recopy notes--or to do so only when clarity and conciseness demand it. Finally, they should review their notes for about five minutes on the same day that they take them, and go over them again for about half an hour at least once a week, according to a regular schedule or play. There are no course syllabus to be memorized instead, the examinations will be based on the material presented in the lectures and textbooks. What is the main idea of the first paragraph?