Many researchers believe that one of the best ways to learn a second language is through immersion.
That is, you speak, listen to, read and write the new language all of the time. Of course, this can be hard to do if your family and friends speak another language most of the time. But whenever you can, try to practice your second language not only with co-workers, fellow students, professors, salespeople and doctors but also with family and friends. Try to see the English language as your own rather than a foreign language. After all, now it is your language.