The title of this thread reminded me of my experience learning Japanese. Living in Tokyo helped, of course. One thing that I had learned about language by then is that you don't just use it to communicate, but to organize your life. (I did not believe that all thought is language, but language helps.
) So I started talking to myself a lot in Japanese. In public I would whisper or talk silently in my head. "Ima aruite imasu. Sore wa basu desu. Sore wa koban. Hi ga akarui. (Later I learned to call the sun taiyo, and to say mabushii.
) Gohan tabeyo ka?" Etc. These days I guess you can walk down the street talking to yourself and people will think that you are on the phone. 
Later I learned that self talk is a stage of language use that children go through at around seven or eight years old. Kids that age talk to themselves a lot.
I also bought Japanese dictionaries (kanwa jiten and kokugo jiten) rather than relying on Japanese-English or English-Japanese dictionaries. I had the latter, but avoided using them if possible. All Japanese All The Time, right?
I read books aimed at children, with furigana. I read manga. That had a strange effect on my language, but at least I never went down the sidewalk saying, "Doke! Doke!"