That is a good question. I think you can refer to Tomlinson (2012)'s book to understand it further.

I think that an important key to succed is to listen to native speakers of the target language and of course to repeat. In order to improve pronunciation the person should record while speaking and then he/she can listening

Phonetics and immersion program. (See Krashen’s work in applied linguistics, ‘Principals and practice of second language acquisition’ and recent work by this scholar)

You can be a model for your pupils.

I don't think it is a must to be a native like... let the pupils try pronunciate Eng. According to their accent, and don't burden them with ideal proninciation. This way hinders their learning process.

You might expose them to English movies and songs. This way, they can listen and copy the accent.

We want our ESL learners to be users not native speakers.

To improve pronunciation: should be recorded while speaking the word/phrase and then listen to the result, and continue to do so.