Use a cell phone application to identify a song and its artist. Various applications require you to hold the phone near the audio source so that the phone "listens" to the song—it will then identify its artist and title for you. If you don't have access to this technology, however, there are other options.
Call the radio station that played the song. If you heard the song on the radio, take note of the time it was playing—many radio stations keep a log of what song titles and artists they've played recently and at what time. Do it sooner rather than later, though, as these logs often don't extend more than one or two days into the past.
Jot down any lyrics to the song you can hear. Try to get at least one or two lines. Enter the lyrics into an Internet search engine. Use quotation marks around the lyrics. By doing this, you are telling the search engine to search for those exact words in those exact order.
Enter the word "lyrics" outside of the quotation marks. This signals to the search engine that you are looking for song lyrics containing the exact phrase you entered inside the quotation marks.
Click on the "Search" button and look through the results. If the lyrics you searched are a common phrase, such as "I love you," then you will likely find a variety of results. Something unique, however, will have less varied results—possibly narrowed down to just one song: the song and artist you were trying to identify.