Make sure you have a good understanding of the standard library - in C, this should not be thought of as a black box (because, unlike in some languages, it is w

Make sure you have a good understanding of the standard library - in C, this should not be thought of as a black box (because, unlike in some languages, it is written in the language itself, and also it's rather small and minimal). You should familiarize yourself with the source for a C standard library (not necessarily the one your're using, maybe uclibc, something simple), and work towards being able to implement the functions yourself. For some functions like malloc(), printf(), etc, understanding the implementation tradeoffs will help you understand problems with your own code.