Use your lecture notes as a guide to your reading in the textbook. Write your questions down if you don't understand something. Ask your instructor if you don't understand a concept.
Make flash cards of definitions, concepts, reactions, structures, and nomenclature that are in the textbook that are emphasized by your instructor in lecture. Writing something is equivalent to reading it ten times.
Do all the homework problems with the aid of the study guide or answer book.
One of the best ways of learning is to find a study partner or to form a study group and work on problems independently and then together.
Keep up to date. If you get two weeks behind or you have a poor grade by midterm you may want to consider dropping the class.
Seek course advice from science professors and students.
See your instructor for a tutor.
Try to see the "big picture"; try to see how the topic of the week fits in with the whole course. If you can't see this, ask your instructor.
Practice applying what you have learned in class to the world around you.
Try to foster your own scientific curiosity - wonder why things are and how they happen.
Have a positive attitude.
Realize that science requires more self-discipline than many other majors, but offers more rewards.