Here are some notes I found today on writing for radio from a course run by Jessica Dromgoole
What is the territory of the play?
You don’t want to be told off by radio, better to think in a more open way about the central question you want to explore.
What is the central narrative Question.? . Then create a character who would answer yes, and a character that would answer no
Structure helps you tell the story. Big events can happen against very mundane things.
And who is the intended audience ? Understand the slot you are writing for: the 45 minute afternoon play? the 60 minute Radio 3 experimental drama The Wire? Play of hte week on World Service (about a demographic. such as gender identity)A 45 minute radio play can deal with 5 or 6 characters.
Put your neck on the line, be brave and authentic.