listen & learn
when you try, relax, & don't give yourself too much pressure when immitating proper english... cus if you "try too hard", you'll just end up stuttering~ just practice more & let it try to flow naturally.
to me, most of the time accents happen because you're still not comfortable & not going smoothly with the dialect...& you are unsure of how to use the vocabulary. improper grammar is also a major cause.