Record yourself speaking and listen for mistakes. Hands down this is one of the best ways to improve your spoken ability in a language (even your native language if you want to avoid umms, and ahhs and so on).
Find a recording of a native speaker that has a transcript.
Listen to a section of the recording.
Record yourself saying the same thing.
Listen back to your recording for mistakes and problems.
Repeat the record/listen cycle until you are happy.
Move on to the next segment.
Finally the most important part and key to the whole thing: do it every day. If you do 30 mins of this a day then you'll notice minor improvements after about a month and significant improvements after about three months.
Use a tool like Audacity: http://audacity.sourceforge.net/
Find a recording of a native speaker that has a transcript.
Listen to a section of the recording.
Record yourself saying the same thing.
Listen back to your recording for mistakes and problems.
Repeat the record/listen cycle until you are happy.
Move on to the next segment.
Finally the most important part and key to the whole thing: do it every day. If you do 30 mins of this a day then you'll notice minor improvements after about a month and significant improvements after about three months.
Also, a shameless plug, check out http://www.chinese-forums.com/ which has a load of advice for learners of Chinese.
And my own tools for learning Chinese:
http://www.imralsoftware.com/