Make a note of the song lyrics. Try to remember as many of the words in the song as possible.
Type the lyrics into a search engine. The search results should reveal the song you're looking for on a music or video website. The title is provided in the header section of the returned results.
Use a song lyric website. Song Lyrics allows you to search for any song using the lyrics, artist or album. Put in as many lyrics as you know and it returns all the songs that contain the same phrases.
Post a query to a lyrics forum. In some cases, an Internet search may not be enough to find the title of a song you wish to download. When this occurs, post all information you have about the song to a forum like All the Lyrics. Members will post answers to your song query.