Log onto the Internet. Using your favorite search engine, type in a memorable phrase or lyric from the song. Use quotation marks around the phrase to increase your chances of finding it online.
Call the radio station to request the play list for the specific date and time of day that you heard the song. Some radio stations have this information listed on their website, so check online too.
Ask a friend. If your friend has similar music tastes, he may have already heard and identified the song.
Tune in to the radio. If the song is popular with listeners, it will be played again. Listen to the radio as often as you can and chances are good that the song will be played again. The disk jockey will usually announce the singer before and after the song is played.