The best way to learn English depends on the person. I personally try to do a myriad of activities, such as: reading in English, watching TV series, listening to music; just to mention a few. What is important is that you put *interest in it* (can't use interest this way). In addition, due to recent technological breakthroughs, (nowadays = weird word /informal) we currently have the opportunity to interact with both native English speakers and people who are also eager to learn the language.
The best way to improve your English, would be to live in an English-speaking country. This will allow you to gain more experience with the language, as you will be exposed to English at all times. Additionally, having a close relationship with someone who is fluent, will also help your fluency in English grow by leaps and bounds.