Read something aloud but in slow speed. Atleast half an hour reading a day is must for the cure. Secondly do some breathing exercises for half an hour more.
Third exercise is similar to breathing exercises but it is meant to cure stammering.
Speak the first sound of the word long......Extend the first letter of the word as much as possible , then just before your final breath, speak the remaning part of the word normally . For E.g DOCTOR
Say it like this Do-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-ctor . That's It.