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Once you're past syntax and basic concepts, he best thing is probably just to write programs. Maybe try some libraries out. And when you do something you've never done before, (at least on small scale things) do a plan that's all your own work (and things from the docs), and then refer to google, stackoverflow etc. when you have problems that you can't figure out.

As well as that, look into some of the advanced language features and idioms, and try to use them in your programs, or rewrite old programs to use them.