If to speak about some technique to learn C/C++ then for example you can try to resolve problems that are described by users in this forum. It will help you to understand what you do not know and what else you should to learn in C/C++.
I think that he best way is to try and fallow some tutorials from the web/youtube, after you get a basic grasp of how c++ works you can start reading some books on the matter. That is how i learned.