Listen and copy. Record your voice, listen to the difference between your voice and that of a native speaker, then record it again until you are satisfied. The key to good pronunciation is listening and practice. The other important thing is to not listen with ' an Italian ear'. For example, an Italian learner complained last week that the English words 'us' and 'as' were the same. They're not - they are completely different sounds in English , but he couldn't 'hear' the difference because he was 'filtering' his understanding of English through his idea of Italian phonology. Try to listen to English with an open mind, not a mind that has been conditioned by your own language. And once you can 'hear' English well, you'll be able to pronounce it well too.

Listening to the radio, listening to films, and to audio clips on English language sites. practising with other students. Find things you like though rather than just anything. You can take some lessons too. You can practise speaking with English speakers. You can find them here:)

Something that's helped me with my French pronunciation is singing in French. It's a great way to learn to mimic proper pronunciation and you don't even notice that you're learning because it's fun :)