One of the biggest mistakes that I've made in studying languages, is to focus too much on just one study method. It's tempting to put all your efforts into one activity, especially when your "new approach" seems to be working!
So why then, does it seem to be working well in the beginning, and not so much later on? The answer is simple: Your leap forward was due to changing your method, not the new method in itself!
When you dedicate your energy on just one thing, learning is slow and difficult. Have you ever been frustrated over seeing the same word or grammar concept again and again, recognizing it as something you should know, but not really knowing it? And then suddenly you listen to a radio show, and the speaker uses the word, and suddenly it just makes sense, as if it was magic?
Barry Farber wrote in his 1991 book "How to Learn any Language"that "seeing a word or phrase in your grammar book fifty times does not secure it in your memory as effectively as seeing it two or three times and then coming across that same word or phrase by surprise in a newspaper or magazine or hearing it on a cassette or in a radio broadcast or a movie or in conversation with a native speaker." (come read my review of "How to learn any language" by Barry Farber)
What goes on in the brain?
The brain treats info that you only get from one source as less important. It doesn't matter if you try to remember it, you can't convince your brain that it's important before it sees the proof. Seeing the word for the first time might create a new connection in your brain, but you need a whole web of interconnected neurons for the learning to really consolidate.
When you think about it, words that you know well, you know lots of things about them. Let's take a random word - say, the French word for "agreement", "accord". Other than agreement, the word also means "chord". This makes sense, because in music, a chord is an agreement of notes. The word is masculine. I know that because I sound out "Un accord" in my head. I can even go further and look at my own associations to the word "accord" - "un accord" sounds like "ana kort" which is a woman's first name and the word for "short" in Danish silly, but to my brain it's information related to the word "accord". When I visualize the word "accord" I see a couple of well-dressed businessmen shaking hands. It rhymes with wart and snort. I could go on an on.
Now, compare this to a word that you struggle to remember. I always forget how to say "shoe" in Arabic, even though it has come up several times when I read Arabic books on my tablet. The dictionary tells me that it's "حذاء" or "Hida'". Listening to this word, it vaguely reminds me of shoes, true, but it doesn't make me feel anything. It doesn't remind me of anything and I don't know any related words. Is a horse-shoe also some kind of "Hida'"? How do you say shoemaker? It is clear to me that my brain doesn't see the Arabic word for "shoe" as something that's interesting enough to play with. It hasn't worked out any silly rhymes or figured out any relationships that the word for shoe might have to other words. So, what If my Syrian friend decides to speak to me about the new shoes that he just bought when we meet tomorrow, or if a news-podcast that I'm listening to, will get into something shoe-related? Three separate instances of discovering the word, will probably be much more effective than coming upon it 50 times in the same book. (oh, and after writing this blog post, don't worry about me forgetting the word "حذاء" again!)
How should you study as a beginner, then?
The trick is to never just do one thing. Variation is extremely important to remembering words as a language learner. Even as a beginner, it's important to mix things up. It may be that your Assimil is the only thing easy enough for you to understand, but it doesn't matter.
In the beginning, while studying your beginner's book, try also deciphering some tweets in your target language (here are some French celebrities that you might want to follow). Maybe just one per day, it's only 140 characters, so it can't be too much of an effort. The words you don't know, you can look up, or simply ignore. The thing is that you'll see some of the words that you vaguely do know, and simply by recognizing it, you'll make it grow roots.
You also need to listen to native material from the very beginning. Assimil and the other beginner courses may be comfortably slowed down, but real-world speech will be a chock to you, if you don't start getting used to it.
A site like Euronews exists in 13 languages. On Euronews you can find news articles on a wide range of topics. Most of them are accompanied by audio or video that more or less follow the text. Some are more complicated than others - if you're a complete beginner, I recommend that you pick very short videos - preferably under one minute. Articles about sports are generally written in a simpler language than politics. Read through it, perhaps with a hover-over dictionary like this one for Mozilla.
Listening to music for language learning variation
Music is also a wonderful way to learn in the beginning. Especially because you easily learn a song "by heart" and therefore will have the lyrics readily available in your head for reference later on. Learning a song without really knowing the meaning of the words is really, really helpful, because the unknown words will follow you around in your head while you do other things. When you stumble upon words that you know from songs, it can be a great eureka moment. I'm currently learning Algerian Arabic through music.
Try to do a little bit every day. In the beginning, you can work with native material, say, 10 minutes per day, while focusing on your Assimil or other beginner course. It can also be helpful to do several courses simultaneously. I just happen to prefer to move on quickly to text and audio designed for native speakers.
As you progress with your course and your daily dose of real-life language, you can start to do more in your target language, but don't push yourself too hard. The essential is that you attack the language from multiple fronts at the same time, in order for growing roots in the language and forming a tighter and tighter network in your brain. It's all about using variation for learning the language.
From beginner to lower intermediate and upwards
When you start to feel that you're getting somewhere in the language, you might want to start to speak and write. But only a little, mind you! In my opinion, output is not at all essential to language learning. It's more a question of performing what you already know. But sometimes when you struggle to find a word to use with a native speaker, the whole situation in itself can be the thing that creates a new connection. You can use words that you vaguely know, and it might help you to getting closer to consolidating it. But you can not use the ones that you don't know at all!
Whenever I speak with a native speaker in Arabic, and they suggest or explain a word that I don't know, I am almost certain that I'll forget it immediately, but I'll also recognize that this might be the beginning of acquiring a new vocabulary.
How do you find someone to communicate with? The web is full of sites facilitating language exchange. Here's a subreddit dedicated to language exchange, but use google if you don't find what you're looking for. Lang-8 is also an extremely helpful site, where you post your writing for correction by native speakers. Don't forget to correct something in your native language too while you're there, though.
Eventually you may start to focus primarily on reading and listening to native material, like articles and blogs about subjects that interest you, or even novels, audio books and films. I've written more in depth about learning languages by reading that you might want to check out.
I hope you found this article helpful! Please throw a comment below if you have something you'd like to add or any other commentary.