Well i personally dont think anyone needs serious courses in accent nuetralization to improve ones english accent. I think interaction with native english speakers is definitley the key.
Watching major hollywood blockbuster films is also is another alternative but one fact wchich almost every one neglects is ” Subtitles ” having english subtitles does a whole lot of difference. You not only see the text, but in the mean time you also develope proper pronunciation. Making recording s of ur voice in english and listening to them is another idea well worth investing some free time in.
i would say voice chat in some american rooms…interacting with local american on the web is another very good way to improve ones accent. It is not only an interesting experience but very very helpful too. As it has been my personal experience.
I think in general most people do have usually a vague idea of how proper american speaks. Watching cnn has already been recomended by most people. I would take the mornings newspaper and try to read it in a way a way that a normal cnn reporter reads. You can actually feel the difference after spending 2 hours on cnn every other day. These other measures are usually very interesting and usually results are very good. One can know his progress by web talking with americans on chat and see if they can tell the difference that u are a Foreigner or not.
Ofcourse there is the fact that proper courses will help a lot. But every little bit makes a huge difference
Just my humble opinion.