That's one way but I've found that the best way is this (and I swear it works):
Watch tons of Bengali tv shows and movies with english subtitles. loll...i know that none of us have the time...but that's the only way you can immerse yourself in a Bengali "world". THEN go and find a native who will teach you because by that time you will already have some working vocabulary and phrases.
I hope that helps. i know that it helped me learn Hindi and I'm now learning Korean in that way.