A telephone call-in show can spark a broad range of topics and involve a widely diverse audience. Examine the demographics of the broadcaster to find out whom you'll be reaching. Then gear your program to that audience. Radio and TV stations, by law, must provide a certain amount of public service broadcasting. Therefore, they may welcome your programming ideas.
Cable carriers have public access channels which have been mandated for public use.
Public access studios come equipped with the necessary technicians. In either case, you will have to reserve your time far in advance and ask stations to provide the technical support to produce the show. Write to station program directors very early requesting their help. For starters, see the sample letters provided.