Practice, practice, practice
I have always been a fast talker. I guess I figured I needed to get whatever I wanted to say out quickly before someone else started talking. I can't stand it when you are in a conversation and two or more people are talking at the same time! I am practicing talking slower and pausing more often. I find that I am not as tense and that I manage to say things in just a short a period of time because there is less stuttering.