Although I might not be as fluent as people who actually communicate in English since there were young by I have several tips to share that may help someone to get started:
Remark: I attended an international school from 1994 - 2004 so this might helped me in accelerate the process but I think these tips will help people who wants to be fluent in English
- Don't be shy
Don't worry about your accent. People have accents. If a foreigner speaks to you, you speak back. No matter what others will say about you. In my country, people who always speak English if their got a chance is seen as artificial and unnatural. Who cares. You won't go anywhere if you let these people into your head. Just remember, you want to be influent and you simply got to practice more than others
- Surround yourself with foreigners
If you are sent to an international schools or abroad, do not stick with your local communities there. I saw many of my friends graduated from fancy universities abroad and yet their English didn't improve at all. They hung out with their Thai friends, go to Thai restaurants and even partied at a Thai clubs. You are there to learn and by being too collective will not help you get anywhere. Unbind yourself and join up with other foreigners. This will force you to learn English faster because you have no way to communicate without improving yourself.
- Watch films without a subtitle
This one is my favorite. I have a box set of Friends (US Series) which I watched almost everyday to improving my english. First start watching it with subtitles, and If you are ready, try watching it without. Although you won't be able to understand a lot at first but as you keep watching over and over, you start memorizing lines and match it with the meaning you understood while you watched it with subtitles and you will start to understand each sentences better.
- Be observant
Watch how people speaks. Start observing how people speaks to each other. What kind of greetings they used, what's appropriate and what's not. A few months ago I started to realized that I have been pronouncing the word Amazon all wrong. I used to pronounced it like Amazing where the emphasis of the word is on Maz. After watching an interview about Amazon CEO, Jeff Bezos I realized that the emphasis should be on "AM"azon rather than a"MAZ"on. Be observant and you'll start to see tricks that can help you speak better.
I hope this helps!