The most direct path to success in this course is to stay caught up with the work. Since mateial builds on the previous topics, if you get behind it is difficult to catch up. If you find that you need help outside of class there are a variety of resources available. Each section has one or two TAs who will be offering a weekly clinic to review material and answer student questions. In addition, you can arrange to meet with your section's TA(s) on an individual basis. You should also contact the instructor for help.
You may also find it helpful to read other textbooks; it is sometimes useful to try different presentations of the material.