My story, may provide you with a few ideas. But I also believe that besides the effort put by self, a bit of guidance from a professional will help you to handle the initial failures and skepticism.
I had a serious stammering problem in my childhood. I still have them when I loose control due to excitement but those situations are few. In class VII I moved from a vernacular school to an English medium residential school. Needless to say first two years I was embarrassed to open my mouth. Then my English teacher (Rao sir, RIP) put the following regime for me:
- pick up an English novel and finish it in two weeks and create a single page summary of whatever I read. Obviously I started with Enid Blyton and then slowly moved into Frederick Forsythe, Robin Cook level and then higher like Kafka, Le carre, Rand etc. This helps you to recognize the sentence construction varieties and introduces your sub-conscious mind to conversational sentences.
- Spend one hour daily reading aloud from any English book - does not matter if you understand or not. Any phonetic problem due to a word, look-up in the dictionary with phonetic symbols and try to pronounce it with the help of Sir.
- Make it a habit to listen to English news from both AIR and BBC (during my time the TV had just started and my school did not have one)
-Watch all English movies sincerely that were screened in our school on weekends. We watched a lot of British oldies as well as old Hollywood ones
-Take every opportunity in the class to speak/present in English
By class XI I was winning in inter-school debates and extempore speeches
Also remember that I was good in English writing, so I had only one enemy to conquer - fluency and diction and use my stammering to provide some importance to specific works in a sentence.