Find a consequence free situation (ordering at a drive through, or asking a question at a mall kiosk or store, reserving a room at a hotel and later canceling, anything where you know you wont be fluent) and say everything you want to say the way you want to say it. That means no word switching, no delaying with um and uh, just speaking exactly the words you want to say and stuttering when it happens. Make a note of how you feel afterwards.