Speaking like a native

yes! i've met a few koreans and heard of others that have never left korea yet speak like native english speakers. it can be done but takes a LOT of hard work.

Do you know what kind of strategy did they use?
Any learning method?

im not sure... but i imagine that they have a natural talent for languages in general and also have good study habits. plus, you'll see students who start learning english early make big strides in their language acquisition.

Chat with native speakers... often.

Yes its possible. A good idea is to feel the language by living it in your own home.

English TV, Movies, podcasts, Newspapers, Magazines, writing, friends ...
Absolutely everyday. All the time. Non-stop.🙂

A good source of news and magazines stories is http://www.jamaby.com
checked for students.

A good source of podcasts is http://www.englishcaster.com

DVDs turn on the English subtitles (text). Turn off your own language.