HI mirza,
The best way to practice for listening comprehension is to listen to the US spoken accent as much as possible. You can tune into american radio channnels like Voice of america. If you have continuous access to the web, goto following link
http://www.voanews.com/real/live/newsnow.ram
But this requires you be connected to internet and also realplayer is necessary.
First hear a part of the news, and practice writing jist of same on a piece of paper.