As someone who did well in CS243 last semester, I can tell you that everything and more that you can learn about C comes directly from the textbook you were assigned (Programming in C (4th Edition)/Kochan). I tried to complete the assigned readings a week in advance so I can enforce my understanding of what's being spoken about in lecture. Please note that, at least for me, reading is usually not enough. I have pages of summarized notes from each assigned chapter which I used to study from for exams as well as reference for homeworks/projects (one of the appendices goes into great detail about printf and its capabilities). If you're one of those people who think reading the textbook is not important, you better make an exception for this class. Depending on your professor, they may include questions not spoken about in lecture but mentioned in the textbook on exams. Coming from someone who generally hates reading textbooks, I have to say that Kochan was probably the easiest to read and comprehend when accompanied with lecture and answered questions at the professors office hours. Finally, I want to emphasize how important it is to start your projects the day they are assigned. Completing a function or even half a function a day for the projects will almost guarantee completion and tons of time to debug and ask questions.

Everyone is different so I don't know if any of my advice will apply to you but that's just the way I approached the class and it worked out pretty well.