shidifen,

Just off the top of my head:

1) Make Chinese friends. Practice with native speakers--plus time--will take you far; it's also great motivation.

2) 1-on-1 tutoring may be more effective than group classes. It means more native Chinese input, at least.

3) Get a good dictionary - pleco.com (with the paid addons) can't be beat.

4) Good textbooks can be helpful in the beginning. I used the New Practical Chinese series (with audio CDs!) when I started. It was good for teaching me my first characters and breaking the sounds of the language down by pinyin syllable.

5) Listen and watch stuff in Chinese that interests and entertains you. Cartoons are good for beginners because the plot can be inferred even if you can't follow all the dialogue (I watched 喜羊羊 when I was starting out). The podcasts at Popup are great for that too, because they're well-produced and funny.

6) Become a paid subscriber here, if you're not already :) Study the Absolute Beginner podcasts on your computer, looking at the transcripts for all the characters you don't know.

7) Download the Popup audio collection to your cell phone (or iPod) for additional listening practice when you are out and about.

8) The Popup Review is helpful for reading Chinese, but you might get more mileage from SRS flashcards for writing. I use Anki, which is free.

9) Don't use Rosetta Stone for learning Chinese :)

10) Be patient and persevere. If you're a native English speaker, the learning curve for Mandarin is much steeper than, say, French. Learn those characters and get your tones straight--it gets better.