From my experience of been involved, in a small way, with a radio program I would say, 1, Make sure your brand/style of music fits in with brand/style of music of the program. We played a loose colection of Traditional/Folk based material BUT lost count of the number of Rock/Pop/New Age/Tartan & Heather CDs sent in. 2, Get a contact name. The presenter may not be who decides what is included in the play lists. The weekend show I was with was presented, produced and engineered by the presenters BUT during the rest of the week playlists were supplyed and for PPRS reasons were strickly followed. 3, Send a CD. Not tapes memory sticks, cassettes or any other fancy gadgets. A CD, your name, address and contact number, any puplicity material and details of where you are playing.
If you do your homework and are any good and worth hearing you will be played.