There are a lot of techniques you should do in order to improve your English pronunciation. Here are a few tips:
To improve your English pronunciation, you should be surrounded by English everyday or in an English speaking environment. If you can't have this situation, you can listen to English radio, or TV, or some CDs in English.
2.Listen and don't speak
When someone talks to you or to someone else in English you should not speak at the same time, you should listen, focus on his speaking, his English intonation, which words he stresses, which words he doesn't stress... Never speak when listening to English, always focus on listening first, speaking will come later!
3.Learn English subconsciously Never try to learn English in a short time. Always listen to English and be sure that you will speak it one day. You don't know exactly when but you will learn it.
Always listen to English and don't try anything else, you will learn English subconsciously for sure.
4.Focus on listening
If you want to learn English or to improve you English pronunciation without listening to English pronunciation, stop right now!! You won’t know what English pronunciation is if you don't listen to English.
5.Speak slowly Never try to speak fast, always try to speak English slowly at the first time. You will get faster subconsciously without doing anything. You should pronounce each word correctly. That's the goal!
Always practice your English every day, read out loud, and speak English with your friends. This will help you to know the correct way to stress syllables.
7.Speak out loud
Never be quiet, always speak out loud. This helps you a lot if you are shy when you speak English.
8.Record yourself speaking English
And compare your speaking with a native speaker, you will see the mistakes you've done. You will improve your English pronunciation.
(taken from various sources)