A radio play can travel through time and space, between centuries and continents. All this can be done for a fraction of what it would cost to do the same in film. But in every case the audience has to be attracted, and its attention held, by the means of sound alone. Good dialogue is not simply a matter of stringing together different conversations - every bit of speech must help the plot move in some direction, increasingly involving the listener as it does. In addition to speech, the writer needs to think about sound effects, music, and, something rarely appreciated by the inexperienced writer, silence.
Pauses also help listeners take in what they have heard and help prepare for what happens next.
Themes You can write on any subject that tackles the lives of Africans. Your play can be set in the past, present or future. Try not to cram too much in, whether in terms of events or ideas. A radio play has scenes like a stage play, but these can be swift and fragmentary, as well as long and solid. It is useful to think of a scene as a sequence.