For a while I was developing a stutter so bad I couldn't talk on the phone. It's gone away now, for the most part. My doc told me it was actually a dyskinesia effect of the lips and tongue.

I practice reading aloud, both with and without a cork in my mouth. The cork forces you to enunciate more fully - try it and then see how well you read the same thing immediately afterwards. An old acting trick....

For writing, first of all I got rid of ballpoint pens because they make you grip, and I practice calligraphy, practicing relaxing during the strokes of the letters.