Rote learning kanji and vocabulary is fine, but excessive reliance on flashcard-based learning has the risk of missing the proper context for words. For instance I tried to use the word 「焦燥」(impatience) in casual conversation, only to discover that it is a word mostly used in literature.
Reading more is helpful, but can be challenging
I believe that there is no silver bullet to language learning, but that you should rather have a healthy mixture of different approaches. One such approach is spending time just reading Japanese, to get exposed to how words are actually used. The biggest problem for me here is that I find it difficult to find text which is both the right level for me while at the same time of a subject matter which I would find interesting. As an example of something interesting but at the wrong level is a pop economics book I once read. While interesting for its subject matter, it was so difficult that I took months to finish reading it, spent most of the time just looking up words.
Why go with a bilingual text?
Reading bilingual versions can be helpful here, ones where the same text is displayed both in English and Japanese side-by-side. It becomes much easier to look up words, when the answers are right there in the English version of the text. You can find a lot of bilingual books in bookstores, but limiting your selection to only those makes it even harder to find something you might be interested in. The best one I found was the movie script for Pulp Fiction, written both in Japanese and in English on the same page spread, but I would rather read about geekier topics.
Bilingual blog articles
If you can't have it in book form, go online instead. Besides printed books, some blogs also have Japanese versions available.
For software and startups, here are two great ones:
Joel on Software
Perhaps not as well-known recently, but Joel on Software was a must-read for software development, also covering topics on management and business. Many of Joel's articles have been translated to Japanese as well, on the Joel on Software in Japanese site.
For startups, Paul Graham (AKA pg) is perhaps the most famous essayist. Many of his writings have Japanese translations available as well.
With a bit of creative Googling, you can find them all: site:http://paulgraham.com/ "japanese translation"
Thanks for reading
If you know more, please let me know.
Bonus: Derek Sivers has his post "To hone your writing, hire a translator" also available in Japanese.