Uma coisa interessante que vi para passar o "intermediate plateau" (aquele desânimo que dá quando se está no nível intermediário de aprendizado de algo pois aprendemos pouco e cometemos os mesmos erros) é aumentar a nossa motivation. Tenho algumas dicas, e fiquem a vontade para mandar mais:
Speaking, Listening : Listen and sing some music, try to memorize them and after read the lyrics and sing with the song; Speak with a friend only in english 1 day per month (it would be like "the english day");
Reading: Read some comics; Read some funny histories (there are a lot of blogs with it!);
Vocabulary: Read a entire (good) book without the dictionary and try to recognize the words that you don't mean in another context (after some pages, maybe);
Grammar: Open the dictionary in a random page and read the first and the last word. (actually i don't have a funny method to learn grammar, so I will be happy if somebody help me on it);
Writing: Translate some text, lyrics, comics (that you like) to english; Write every day something that you liked or you will do (e.g.: I'm going to a party and I will dance trough the night; I watched a funny movie called "Como se fosse a primeira vez"), just simple sentences because will be easier to do and you can do it EVERY day;
Any other suggestions?
That's all folks