“Hello caller — you're on the air!” This is a fundraiser that will have you working closely with a local radio station, giving them help in selling advertising time for one particular day. It is likely to involve a lot of work on your part, but it can also raise a substantial level of funds.
First and foremost you need to find a station that's happy to work with your group. Then you need to decide between yourselves what percentage of the advertising takings will be going to charity and how much the radio station gets to keep.
Get together with the staff in the sales department at the local station to get lists of advertisers and make contact with them. You might find some staff can give you advice and pointers, and they can also help you decide on the advertising rate you're going to set (it doesn't have to be the normal rate).
As you have more flexibility than the radio station does, you can be more creative, and you may be able to get advertising from people who otherwise wouldn't be able to afford it. You might want to let individuals from your community to sponsor specific songs (and add a dedication). The station involved might let you read out some of the advertisements live on air — try and get everyone involved who wants to be.