You will not attend to, understand, or retain lecture material if you approach lectures in a passive manner. Go to class prepared to actively learn the material that will be given in the lecture. The vast majority of information is forgotten very quickly if it is not practiced. If it is practiced on several occasions, it is much less likely to be forgotten. The more familiar you are with a person who is speaking to you, the more able you are to interpret his or her message.
People understand and retain organized material far better than material that is unorganized.
This will be harder during some lectures than others, but it is extremely important that you do it in all lectures. The information that your professor presents in lectures is as important as the material from your textbook.