I think if you wanT to speaking english. you have to feel confidence about yourself eventhought you not good. don't worry about mistakes when speaking. just make you have a habit for useing english.

Thank you all, your comments really help

Listenning to English music, speak English as much as possible, buy a small oxford dictionary to bring with you easily, watching movies, films, and try to hear what they say on this film to improve your English. 

Listening a lot and doing shadowing to improve your speking, that also works. 

Just talking to others doesn't help to improve your speaking skill. 

If you have a plan to have langauge exchange partners, it's better to ask them to correct or point out your mistakes otherwise, you just waste your time. 

I mean, if you don't ask them to do so, most of the time, they don't say anything since they feel bad for you or don't want to interrup in their conversation by pointing out your mistakes. 

By practising it as much as you can. At first it may be a bit hard but if you talk to native speakers every day, it will be natural after a while.