I think pinyin is very useful for you to study Mandarin. Pinyin can improve your pronounce and you can use pinyin to typewrite the Mandarin or Cantonese in your PC, you can msn with Chinese easy. pinyin is good for you.
I think more practice is very important for study language.
Cantonese and Mandarin, I think you can see chinese movie and soap opera , chinese news or talk show .