Try not to write everything down. Be concise and sum up lecture material in your own words whenever possible. Write down unfamiliar terms. Review your notes as soon after class as possible. You can fill in details that you missed and review the material while it is still fresh on your mind.
Some professors follow the book closely.
In this case it may be helpful to take the book to class and highlight important topics or terms and write notes in the margins. If you are struggling in your class, talk to your professor. He or she may be able to assist you or send you in the right direction to get the resources you need. However, do not wait until the last minute. Most professors have little sympathy for students who become concerned about failing during the last few weeks of the semester.