<p>Chinese is my first language also, although I started learning English a long time ago. I found that there are two important things that one can do to improve his/her vocabulary and they complement each other. </p>
<p>1). Vocabulary lists: I know it's boring. I know it may seem hopeless. But if you don't have a foundation of basic English words, no amount of practice will help. Start small, 10 words a day. Test yourself everyday on the stuff from the day before and at the end of every week on words learned during that week. </p>
<p>From your post, Alva it appears that you have done this before and do possess the basic vocabulary of English words. In that case, you should move onto more advanced lists. </p>
<p>2). Practice: you must practice speaking and listening. I'm sure this part is infinitely harder for you than it was for me since you live in Beijing, but I encourage you to seek out those who are reasonably fluent English speakers so that you can practice. Try talking to your teacher one on one. Or try to find a place frequented by English-speaking expats and ask to converse with them on a regular basis for practice. I'm sure you will find someone who's willing to oblige. </p>
<p>Additionally, you should read English, preferably aloud if you can. Pay attention to pronounciation, sentence structure, and flow. If you need to know how to pronounce a word, try [url=<a href="http://Dictionary.com%5DDictionary.com%5B/url">http://Dictionary.com]Dictionary.com[/url</a>], they provide free pronounciations. If that doesn't work for you, you can purchase Kingsoft Powerword (金山词霸), a chinese-english/english-chinese dictionary software that includes adequate pronounciations. The easiest way to do this, I think, is to read the news. Try one or two articles a day from sources like the New York Times, CNN, etc. if you can access those sites. Once you are comfortable with articles, you can move onto materials such as magazines, etc. </p>
<p>Finally, if you can access them, watch movies or TV in English. Don't use subtitles and just listen. Try to catch bits and pieces of conversation that you can understand. Don't worry if you can't understand everything, you can often infer plot, etc.</p>
<p>As you keep practicing, I'm certain that you'll find it easier and easier but you must put forth the effort to do these things. Since you said you attend Peking University, I think it would be fair to say that you are a hard working student so I wish you the best of luck in this pursuit. :)</p>
<p>Edit: of course, you can also visit online forums to practice English. But be aware that internet jargon is very prevalent and can be detrimental to those who are trying to learn English properly. Certainly try to use proper English when you communicate on the internet.</p>