Choose the mood for your breakup song. Perhaps you are saddened by a recent breakup and want to write a song with a somber tone. Or maybe you're ecstatic that you're single and can start dating again. Determine the mood you want to convey to the listener. This plays a big role in the lyric content and tone of the music.
Come up with a lyrical hook/title for your breakup song that conveys the overall feeling of the song. For example, if you want to tell a former lover you're done with his lies, you might name your song "No More Broken Promises." Take the theme of your song and come up with a hook that encompasses all of your feelings into something bold and easy to remember that anyone can relate to.
Write verse lyrics that tell the story of your failed relationship. If you're writing a sad breakup song called "I'll Remember You," you might write about happy memories shared with a lover in the first verse (e.g. "The times we stayed up all night long in each other's arms.") Elaborate on the notion of the first verse in the second verse. For example, if you were writing the second verse to "I'll Remember You," you might write about what it feels like to be alone (e.g. "Now I lie alone at night staring at an empty pillow").
Write a chorus that evokes the overarching them of the song and includes your lyrical hook/title. Your chorus should represent the emotional impact that the story in the verse implies. If your verses describe all of the times your ex let you down, your chorus should emphasize the feeling you get from this. In this instance, for example, your chorus might be:
I'm done being let done
I'm picking myself up now
Write a bridge that departs from the verse and chorus, offering a new perspective on the breakup. Say your verse and chorus convey that now that you're broken up, you don't know what to do with your time. In your bridge, you could offer possible answers to these feelings of confusion. For example, you might write:
Maybe I'll take an interstate drive
Maybe I'll just clear my mind
Set your lyrics to music according to the tone of the song. For example, if your song is about breaking up because you found your partner in bed with someone else, it'd be best to set the lyrics to darker music and minor chords. If your song is about breaking up, but remaining friends, you can set your lyrics to something more upbeat with major chords.