Take the time to examine the diagrams and read the associated captions. Make sure you understand the diagrams. Readings assigned on the Internet may have important terms highlighted, indicating not only their importance, but also a link to a definition list. Make sure you understand important terms. Take the time to do the assigned readings.
Some students feel that going to lecture is sufficient and they never open their book.
This is NOT a good idea. When you read the text, read the assigned reading from start to finish, without taking any notes or doing any highlighting. Read the material through to get an idea of the important topics and the direction of the discussion. Next, take notes from the assigned reading using the Internet outlines as a guide. After taking lecture notes, go back to your notes from the textbook and review these notes along with your lecture notes.