Ensure the subject knows what their specific task is – e.g. solving 5 / 0.75, deciding what they will have for dinner, writing directions to the cathedral.

Ask them to say out loud whatever is going on in their mind. 

<> Warm up by reading aloud.

<> Generic prompt to "keep talking".

<> Who is the audience? Imagine you are "talking to yourself" with no one around.

<> Demonstrate it on some examples.