The best way to learn a new language is to practice it! There is no point in sitting in a classroom without putting the language you are studying to good use! So, this is why I believe that the best way to improve is to be in dialect with someone and it is the quickest way to pick up the language! I know this from experience as having been immersed into a New York public school, which is where I learnt the perfect English I have today, without ever learning 'classroom' grammar.