So my honest conclusion is, not only is there no best method, but it almost doesn’t matter what you do, so long as you do a lot of it.  In other words, volume trumps method.   Moreover, what’s effective for an intermediate learner is often not appropriate for a beginner or an advanced student, which means that listening to the advice of others may be a bad idea.  The internet in particular is full of people telling you what’s best:  Read the newspaper in Japanese; switch your operating system to Japanese; use a Japanese-Japanese dictionary.  Everybody’s got an opinion.  Bottom line is, you should probably spend a lot less time reading about how to learn Japanese, and more time actually learning it.  I mean, except for this, which you should read twice.