Learning Japanese

There is an overabundance of information on how to learn Japanese. After spending too much time consuming it all, a combination of immersion + Spaced Repetition Software (SRS) works the best for me:

The most important benefit here is a measurable goal. Reaching a vocabulary of 10,000 words means conversational fluency (you'd know 99% of most common words)

Methodology

To remember 10,000 words use SRS software like Anki
To find 10,000 most common words for your use case immerse and "mine" those words into your SRS deck using Yomitan
Immersion means consuming content in native language (books, series, movies). Immersion is crucial for language acquisition (actually learning the language) instead of rote memorization. You can technically learn a language just by immersing, but an SRS speeds up the process and gives you a measurable goal (not to be underestimated).
To learn fundamental grammar use these weird Cure Dolly Lessons (YouTube, though I prefer the transcript)
For more info on why this seems to be the best way, read this