Open a search engine on the Internet and type in a few keywords or lyrics from the song. Place quote marks at the front and at the end of the words. Type the word "lyrics'' either before or after the keywords that are in quotes. Hit search, which will often direct you to a website that might recognize those words as part of a song.
Go to one of the multitude of websites that are designed to help search for a song by its lyrics. Find these websites by typing "lyrics search'' or "song titles'' into your search engine. Type in any keywords you remember from the song. Quite often a memorable part of a song is its chorus, or most repeated line. Many times this will be the name of the song.
Type in any another information you might know about the song in a search engine. Keywords could include the artist who recorded the song, or the name of an album or movie where you heard the song. Many artists (or bands) have their own websites. These websites include the titles of the songs they have recorded. The words of the songs are often included on the site.