Just food for thought, amikoj. It seems to me that books on languages in general skip over the subconscious and intuitive element which I believe to be crucial in attaining fluency. Children seem more in touch with it, so that they can pick up languages by osmosis just by being in a country for a few months. I have a hazy memory of a hasidic story I read in the 80s, my interpretation of which was that each language has an 'essence', which, if one gets in touch with it, conveys an immediate and intuitive knowledge of the language, possibly the proper basis of the 'gift of tongues'. So, if our minds are properly 'prepared', in theory we can know a language without studying! The nearest we can get to this as adults, perhaps, is knowing the meaning of a word in context without having seen it before or even analysing its components (if it has any). Thus any course is an imperfect model for the 'immersion' which children experience, but how to model their receptivity is a harder one! If there are any neurological or psychological correlates that we can actively influence in our favour that might be very useful.

I think I leart quite a lot of my English unconsciously, because when we had grammar in the English classes I and my classmates always answered the the question "why should this sentence be written this way?" with, "because it sounds right". But a lot of hard work was needed too. I think that ability to learn language that children have disapears when you get older. I have practised and used English for a long time now, but I still am by no means fluent.

One thing I think is very helpful once having attained an ok level knowledge in a language, is to read a lot of books. I began to do that only after 6 years with English, and felt I ought to have done so earlier because it helped so much, even if not opening a dicionary once, and the grammar get stuck once you have read something a couple of times.