I’ve found that each new language must be treated like a unique project. Sure, plenty of methods will carry over. For me, those things will include reading novels and comics and listening to news radio. However, some methods I have used for French, Spanish, and Dutch only prove to be frustrating when carried over to languages that are less related or unrelated to English (my L1).
For instance, I’ve used SRS sentences AJATT-style extensively for French and Spanish, and to some extent, Dutch. But when I’ve tried to do the same thing for Japanese and Chinese, I’ve gotten bored and thrown the whole project out the window (even though it’s exactly the method suggested on All Japanese All The Time). To a lesser extent, this has happened with Polish and Icelandic, as well.
I’ve had to remind myself that with French, Spanish, Italian, and Dutch, I’ve relied heavily on cognates and grammar from English or previously-learned languages. Then, when I make flashcards, I simply define the words I don’t know from the sentence on the front of the card. When I try to do this with other languages, the cognates and grammar are not there, and so the cards become that much more tedious.
Life has been much simpler since I decided to adopt an “anything that sticks” plan. As litigators will often say, “throw everything at the wall and see what sticks.” Convenience is key, because that’s what keeps us working and studying. High-quality materials make us want to study. So, I come at each project with an arsenal of textbooks, reading material, and listening material. Sometimes there are convenient and high-quality radio stations in one language (like Dutch) and not in another (like Pashto). Sometimes reading material is readily available in one language (like Japanese [Book-Off!]) and not in another (like Dutch). Each language has a slightly different path, and it only takes some creativity to see what works and what is convenient.