I'd suggest that you'd take good language course, and when you feel confident you ought to live for a period in the particular region to adapt their dialect.
I think, best way will be to move to the place where the language you want to learn, is spoken.
I studied French language for 1 year in my home country, though I had good grammer,vocabulary knowledge and could understand written French, but when it comes to listening and speaking, it was always difficult because of the French accent. There were some students who were able to pick up very fast as they devoted extra few hours everyday listening to audio,videos and joining the special conversational classes for the language and watching French movies.
I learned German language very fast in comparison to French as I learned it in Germany itself.