Principles

It is not necessary to speak with a perfect native English accent - in fact, a foreign accent in English is often seen as charming! What is vital, however, is to reduce the frequency of any confusing sounds, so that your friends / colleagues / clients / audience understand your message clearly. 

The key to improving your pronunciation is to understand the differences between English and your native language in the following areas:

1. The rhythm of the language.
2. The sounds of the language (e.g. /k/ in keep, or /uː/ in food) and how they join up together.
3. The intonation (pitch changes) of the language.

You can improve each point separately and then gradually bring all three together.