Review the lyrics. See if any word or phrase jumps out at you as creating the essence of the song. You can try playing the song for friends and ask their opinions. The hook of a song is often used as the title. Sometimes, if the song revolves about a particular person, his or her name will become the title.
Make a list of your favorite songs. Think about their titles and how they relate to the song's lyrics and mood. Then apply this to your song. Ask yourself what you felt when you wrote the song. For instance, you could title a song "Angry Breakup Music." Ask yourself how you picture your listeners reacting to the song, or what you expect them to do while hearing it. You could humorously label the song this way.
Write down your ideas for a song title, then put them through a creative blender. Try cutting words from a title that is good, but too long. Experiment with mixing and matching words from a couple of possible titles that don't quite meet your standards.
Imagine your favorite band or singer performing your song in a music video, letting yourself think about the way they might arrange it to suit their style. Imagine their phrasing and what they would be wearing as they sang the song. Then, thinking of that music video as a movie, give it a name that would make people want to watch it.
Say you write a song about a chandelier, and the chandelier gives off light. And the light is the color red, and red reminds you of the color you are not supposed to wear around a bull. So you name the song "Cow." Use the Billy Corgan free-association method. Follow a twisting train of thought related to the genesis or mood of the song until you hit upon the mysteriously perfect word or phrase.