What’s the best way to improve my C++ programs?

That depends on how you use it. Most people underestimate abstract classes and templates. Conversely, most people seriously overuse casts and macros. Have a look at one of Stroustrup’s papers or books for ideas. One way of thinking of abstract classes and templates is as interfaces that allow a more clean and logical presentation of services than is easy to provide through functions or single-rooted class hierarchies. See other sections of this FAQ for some specific examples and ideas.