Enter as many of the lyrics as you can remember into a search engine. If you're certain of the words, put quotation marks around the lyrics to get more relevant results. The search engine usually returns websites that have all the song's lyrics or sites with a video of the artist singing the song that matches the lyrics. Listen to the songs or read the lyrics to find the song you want.
Visit a music recognition website such as Bored.com, Midomi.com or Tunatic from WildBits.com. These sites, which have extensive music libraries, let you find a song by singing, humming or tapping a small section of the music. After the website narrows down the choices, listen to the results until you find the name and artist of the song you want.
Ask questions on music forums or general forums. In your query, provide as much information as you can, such as the name of the television show, movie or commercial that featured the song you liked.