1.Payola for the national day time slots.
2.Network with the overnight/evening Dj's, most of them play club's/parties as well.
3.Seek club Dj's, if the tracks are appropriate for the venue.
4.Also check for community(free) radio and college radio. Literally just introduce yourself/company and state your goals.
I only deal with number 3 and 4. They have never asked for money.