Here’s a rough sketch of my approach to language learning:

• learn the phonology
• learn the grammar
  • read a grammar book like a novel, quickly through
  • read the grammar taking notes, ignoring overly complicated matters. Your notes will be but a few pages long!
• go through a textbook to internalize the grammar, build a core vocabulary and Sprachgefühl
  • read a good textbook (Assimil, good old Colloquial or Teach Yourself) rereading the dialogues and until you remember their vocabularies
  • memorize choice dialogues, songs and poems. Some techniques:
    • just just say just say the just say the whole just say the whole sentence just say the whole sentence like just say the whole sentence like this, to memorize a whole page of text in
    • write the first letter of each word: “w t f l o e w” to use as a crutch when reciting an entire page you learned a few days ago, but remember it’s not important to remember it after, just memorizing for a single recital already etches the words and grammar in your mind forever
    • simply repeat a new word (or better yet, it’s whole context/clause) 30+ times quickly to chisel it into you brain. At 30 seconds a word, you can learn over 100 words per hour, keeping most with you afterwards!
• read
  • we can read significantly faster than people can speak, so reading gives us far higher input for our time
  • read widely, forums, novels, friends’ chat logs, subtitles etc. only looking up words you encounter often or which stick with you, your Sprachgefühl should often give you an inkling
  • Listening-Reading method - the overall fastest way to language mastery at this point, just listen to an audiobook in your target language while reading along to the same book in a language you understand (Dostoevsky, Dumas, Verne and Rowling are easy to find) The longer you can do a sitting, the better. A single 12 hour session will turn your brain to mush, but gift you a huge leap in fluency! The full system

Overall, you want to stay just out of your comfort zone on comprehensible input. Good textbooks are the best way to do this, then reading’s the fastest way to continue progressing. You can start with a textbook before reading a dedicated grammar but I like groking the system early. Phonology is important early on, to develop an inner voice and Sprachgefühl.

Most importantly, an educated native knows tens of thousands of words, idioms etc. Compared to that, learning some conjugations or declensions, some 30 letters of a new alphabet etc. are nothing, a day’s work really. I optimize for the slog of vocabulary acquisition.