I think practicing is the most important way to prove English skill

Read english book and watch english movie.

The most easiest way it's find someone who's english is perfect, and be a friend with that person, just talking and talking on a daily basis will definitely help you to improve your english, plus you should start to watch movies in english with english subtitles, if you don't get something, just change subtitles to your native language 

Gosh, aren't these a weird question, fo sure! The way to learn something is do it until you master it. If you want to learn to speak English, do speak English. If you want to learn to listen and understand, do a lot listening and understanding. If you want to learn to ride a bycicle, go and ride a bycicle, until you don't fall. That's that easy!

I always tell my students to read and watch tv in English (Remove the subtittles is possible).  Believe it or not, it helps a lot specially if you repeat what they are saying.  :)