Firstly, listen as much as you can and try to get the sounds clear in your head. Can you actually hear the same sounds in your head as you do on the TV, etc? I find that being able to create tyhe sounds inside my head is a good first step. At the moment I am trying to learn a language that has many sounds that aren't in my language, and it can be very difficuly to do, so I am listening to a lot and just practising the individual sounds. I start in an exaggerated manner and then try to refine, bringing them closer and closer. Practising in the bathroom in front of the mirror is good because it's private and there's bright light which allows you to see what you are doinbg. Also, from what I have seen with my Chinese students over the years, try not to think of the sounds of English as the same as the words on paper- we change souns an awful lot when we are speaking, running words together, adding and removing sounds to make things flow. Try not to think mof the individual words, but the clusters or groups that they becomes. Many grammatical words are unstressed because we focus on meaning when talking, and can become almost inaudible.