How can I become fluent when speaking English?

By communicating with spoeakers, listening, watchg films and reading 

Mastery of any language is achieved by practice. You could practice English through social media. Join several platforms and engage with members. I have come to learn about one on Twitter known as talklang where you could communicate with members. Subscribe in English magazines newsletters to regularly read diverse articles. Watch English movies without subtitles to gain profound vocabulary. Good luck in your exploration journey:)

A language speaking is like sports, more than you practice more you become better on it.

With my students i used also to look for lyrics in english and start singing.. that keeps you more attention to the hearing.

Enter here

  http://englishlive.ef.com/ar-sa/learn-english-online/english-courses-online/

Speak  to others with out fear of mistake... watch English news and movie and earn daily vocabulary...

with training and studying and listen how native speakers talk   

I have the same problem with becoming fluent in arabic.  I know for a fact that just listening to others speak or watching movies in the english language is not enough.  The mind requires actual verbal practice to establish memory so make sure you have some patient friends who are willing to let you practice with them.

by thinking that you are a native speaker....that we must think the way they use

As mentioned by others,movies,tv shows that are in English, talking to people in English and if you don't have people to talk to, try programs like Rosetta Stone from the internet. Google it, I think it will help you better yourself in English :)

If you wont to be fluent speaker an English usually you should have to be practices with native speakers,or others some one.more over watching movies,and using internet different web sites 

In addition to the previous suggestions, I recommend "Toastmasters Club". there are branches around the world, and they are effective in developing leadership and communication skills; their main tool is speeches.