Read any material to be covered before listening to the presentation. Find the ideas. Discriminate main points from important details. Find the organization underlying the content being presented. Watch for the speaker's signals.
Speakers use many of the same signals used in writing.
Listen actively, not passively. Identify questions you want answered by the speaker. Ask yourself questions about what you are hearing. Make notes, don't just take them. Effective lecture notes are even more important than effective reading notes.