I would agree, definitely practice with a native English speaker. But, also the thing that makes words flow smoothly in a sentence is grammar. So, once you have a good understanding of the vocabulary, start devoting a lot of time to studying the grammar of sentences! It will help make it sound fluid, and also can be fun! :)

If you find the perfect answer to this question, please share it with all of us. We will be eternally grateful. Here is one person's input http://www.youtube.com/watch?v=eFpzeGoP-Kg However I think that you need exposure + practice, especially practice where you cannot retreat into your native language when difficulties arise. That idea is sometimes called language immersion. So find a group of English only speakers and talk to them, or find a group of fellow students and set up some system where you stick strictly to English -- perhaps a small fine for people who relapse to Chinese (you can use the money collected to have a party for people who become fluent :- ) )