Roughly speaking,

You should interact with people who speak the English Language fluently. You'd better make sure that you converse with these people regularly and get a feedback on areas where you need to improve. At periodic intervals, you should also record your voice which will help you gauge the progress you are making. Podcasting seems to be an appropriate option and you could also exchange your recordings with other podcasters.
Right before podcasting, make sure that you immerse yourself in English just before any speaking task, test or lesson. Try to read books, magazines and newspapers in English. Watch British or American films, TV or even listen to the radio if possible.
Paraphrased from:
http://www.teachingenglish.org.uk/forum-topic/how-improve-speaking-listening
For further reading on Speaking tips, click on the word TIPS.