Read a lot! And watch many videos or movies on similar subjects so that you learn how to pronounce those words. Then you could write about the videos/movies, or share your opinions about them online. Extra points if it's something you actually like and know a bit about.
Just a quick warning: sometimes not even native speakers know the "proper" pronunciation of certain words, so you'll hear a variety of accents and pronunciations, from this just pick your fighter, whatever sounds better to you I guess. Also, sometimes people can be mean online, don't mind them.
Source: I got my english from books, games and youtube, then got a bit of practice from speaking with friends and working at call centers.