Language Acquisition
Refold
Refold seems to be an excellent roadmap for acquiring a language.
Acquiring a language vs learning a language
Steven Krashen suggests a better strategy for picking up a second language is through language acquisition. This involves massive amount of input and minimal output in early stages.
Steve Kaufmann is also a big fan of the language acquisition approach.
All Japanese All The Time also seems to follow this strategy to some extent. However, AJATT mainly suggests doing "things that you find fun" in the language (e.g. watching netflix or reading books).
Matt vs Japan is also a big fan of language acquisition (he was big on the AJATT ideas).