Breathing is fundamental to speech. A stammer is caused by erratic airflow, so if you have a smooth airflow, you have smooth speech.
Read the dictionary from A to Izzard today. Get a vocabulary. Brush up on your diction. See whether wisdom is just a lot of language.
I had a dialect coach from the Royal Shakespeare Company who was from Sheffield.
The voice is a human sound which nothing inanimate can perfectly imitate. It has an authority and an insinuating property which writing lacks. It is not merely so much air, but air modulated and impregnated with life.
Reading your own material aloud forces you to listen.
To learn English you must begin by thrusting the jaw forward, almost clenching the teeth, and practically immbilizing the lips. In this way the English produce the series of unpleasant little mews of which their language consists.
I didn't realise I had a speech impediment until I came back to England. I spent the whole of my life working abroad, and no-one mentioned it. I came back to England and suddenly realised I had a speech impediment.
If you have a good ear for dialogue, you just can't help thinking about the way people talk. You're drawn to it. And the obsessive interest in it forces you to develop it. You almost can't help yourself.