Debugging C

Robert Ward, "Debugging C". There is a second edition with a somewhat different title that I have not read, but expect would be good. He emphasizes the use of the scientific method - observe your program's behavior, form a hypothesis as to what the bug could be, design an experiment to test your hypothesis. Just learning to be methodical rather than thrashing around mindlessly helped me tremendously. It's out of print but I expect you could find it on Alibris.