Write a verse or two for your song before the chorus if possible. Different songwriters use different methods of writing. Sometimes the chorus of a song might come to you and inspire the rest of the song. But in general, if you can write a couple of verses first, they may help suggest a good chorus. A verse is the part of a song that sets up the chorus. The verses may tell a story, and the chorus may expand upon the theme.
Example:
I live day to day
Working to make ends meet
I work hard like everyone should
To keep me off of the street.
The above example is a verse. The chorus to this song might look like this:
Everybody has to play the game,
It's the way we survive.
Every day for me is the same,
Just tryin' to stay alive.
Change the melody of the chorus to differ from the verses. The chorus should be a memorable element that encapsulates the message of the song. The lyrics (words) in the chorus should highlight or reinforce the song's message. In the above example, the verse talks about working hard to make ends meet and keep a roof over your head. The theme is surviving, and the chorus reinforces that theme.
Include the title of your song in the chorus when you can do so naturally. The title of a song is important and often a part of the chorus. This helps listeners remember the song better. It isn't a requirement that the title of a song be in the chorus, or even in the song itself, but a rule of thumb is to use it when possible.
Write a dramatic change in melody for your chorus from the verses. The chorus of your song should be distinct from the verses. A good way to achieve this is to modulate up a half step in pitch for the chorus. Another way is to change the melody and rhythm of the notes that go with the words. If your verse has short, punchy lines, consider writing lines of your chorus that include notes held out by the singer. The chorus should be catchy both lyrically and melodically. Think of the famous chorus (used by many performers) that goes, "Na, na - na na naaaa na naa naa . . ." There are no words, but the melody lingers in the mind.