In my work as a speaking skills coach, there are three principles I apply when working with people who want to change their accents. Apply these three principles and you will succeed in reducing or changing your accent.
Awareness – Having awareness of your speech means that you are able to observe the way you speak. You can train yourself to become aware of your speech so that you notice aspects of speech that you want to change. Awareness also means that you are able to observe the way other people speak. Importantly, awareness doesn’t mean being critical of what you observe. You observe like a scientist, not a judge.
Modelling – Find someone whose accent or style of speech you like, for example a famous person. You then start listening very closely to the way they speak. Apply your awareness training here so that you can really notice what you like about the way this person speaks. You can then incorporate what you like about their speaking style into your own speech.
Change Sounds – When working to change your accent, you don’t always need to change every single sound. There may be just one or two sounds you need to change to soften your accent. When you know about the phonemes and sounds of English you can then research the sounds you want to change. Having knowledge of phonemes will save you time as you work to change your accent. It also means that when observing the speech of yourself and others you can precisely identify what you are listening to at the level of individual sounds. When you know what your problem sounds are, you can then research these sounds and how to say them correctly in your chosen accent.