Here are some horrible truths:
Most radio drama is very badly written. Radio drama is an endangered species. It has never taken a hold of mainstream programming on commercial radio in the UK. It used to be the mainstream in the States and Australia but lost out to TV in the middle to late fifties. It is under threat within public radio services including the BBC because of the pressure of monetarist ideology and the fact that authors and radio drama directors have been too complacent. IRDP is a significant oasis and continues to support the principle of the original play.
The beginning is everything. If this part of it does not work you are 'up shit creek without a paddle'. Your listeners will desert you. You have failed. You do not exist as a dramatist. Booo!
The Moment of Arrival
This is how you drop your listeners into the story. Don't give them a warm bed with comfortable pillows and a hot water bottle. The background and sub-text of previous histories is better explored through revelation in dramatic action. So parachute your listener into a top dramatic moment. Not the climax. That would be premature. Find the MOMENT to join the story. Avoid the slow snail's explicatory route. Kick 'em into a high energy trip and whoosh them through the rapids.
Set up...struggle...resolution. You can reverse this if the set-up is more dramatic and explosive than the resolution. Regard your play as a series of phases The Plot
This is the story with lots of twists and turns. The more the merrier. Most listeners like good exciting plots. Without a good plot you're eating a souffle that has gone flat. You need plot, more plot and more plot. Run at least two story lines. Two sub plots would be interesting. Keep the plots linked logically within the same play. The best system is a major and a minor storyline linked to one another. Get them to come together at the end.
People are hungry for entertainment. If they wanted boredom they would be filling out their tax returns instead of listening to your radio play. Make people afraid, but also excited.
Your main character must have the sympathy of the audience. Your audience has to identify with your main character. If this does not happen you have created a failure. Booo!
Drama = conflict = audience. There has to be an emotional, financial, human, moral, physical struggle so your listeners can laugh or cry. Yes, you want your listeners to laugh or cry or laugh and cry. If you don't, give up.
Polarities or Extremes
The art of story telling is exploring the extreme limits of our psychological or physical existence. To pitch one polarity against another.
I apologize for the sexual metaphor. But there is something in this. The better sex has foreplay, development, sustained excitement, surprise and affection, nay love followed by an explosion of ecstasy. Good radio drama is not all that different. If you don't use it, you lose it.
This is how we engage dramatically with the world. Characters inform, argue, amuse, outrage, argue through the ebb and flow of dialogue. When we do we talk and that is how great radio plays are made.....by talking in dramatic dialogue.
Atmosphere / Ambience
This sets the emotional spirit of the play. It determines whether your listeners believe in the world that you have created. Worlds are not created by dramatic dialogue alone. There is attitude and atmosphere. This is determined by detail and relevant detail. It could be in a sound effect. It could be in the writing. It could be in the music. It could be in everything. But the result is that the fifth dimension of radio writing - the imagination of the listener - is stimulated to become a picture palace of the mind.
Got to be there. You have to generate an emotional response from the audience....preferably to the main character....also not so strongly...