Practice? Make fun little apps? Join a team? Get a job with programming? It really depends on how good you are. Here is my main suggestion though, Learn what you don't know :D
Is that a book? If it is you can still check it out, if it is too advanced than you can just stop reading it until a later time when you are up to that level.
Once you have a solid foundation of the basics, maybe you could start to lean towards a specific area of study such as artificial intelligence, physics, graphics, hardware, networking, etc. As for reading material, I've only read (still reading) the C++ Standard, and Programming Principles and Practice Using C++. The C++ Standard tells you more or less everything about the C++ language. The Programming Principles and Practice Using C++ book was written by the C++ creator himself.
Thanks for the help. Don't be to happy though, because as soon as I finish "C++ Without Fear" I'll be here to haunt you with more pathetic questions and problems on sockets ;)