Early in the morning at around 7am- 8am you can go in some garden areas and then take a long breath in as much as you can and then release it slowly until normal. Do this 10-15 times daily. You can do this excercise in the evening too but i prefer morning. If any more queries do ask me cuz because of this i have cured 80% of my stammering Ya and also do talk slowly with everyone not that slow also but slower than your normal speed of speaking