Maybe this is just me, but I've noticed my Mandarin progress take form in some strange ways...
  • You answer you friends with short Mandarin sentences such as "我不知道", "没有" or anything that you've recently learned. They then turn at you thought you were mumbling and then you answer them in the appropriate language.
  • You decide to watch Chinese series in Chinese with Chinese subtitles even though you don't understand most of it.
  • Every Asian person you meet you listen intently hoping to catch some gossip or surprise them with Chinese.
  • You collect Chinese books, hoping that one day you will manage to read them.
  • Your go to phrase when some asks you to say something in Mandarin goes from "你好" to "我会说一点中文".
  • Your birthday wishes to friends, in a bid to be unique, is given in Chinese "祝你生日快乐".
  • You start having internal monologues with yourself in Chinese.
  • You start dreaming in Chinese, baffling yourself in the morning that you understood everything.
  • At night you repeat your favourite Chinese phrase over and over just because it sounds good.
  • You start saying "Good sound" or "Good taste" as a direct influence from "好听" and "好吃" etc.
  • You have set up QQ and started talking strangers in Chinese.
  • You RSS feeder is almost taken over by Chinese Interest and/or Mandarin blogs.
  • You have visited Baidu to search for a interesting Chinese music

These all happened to me, do you have some more?