Four Easy Steps to Writing A Hit Chorus
Songwriting Tips by Molly-Ann Leikin
 
Step One : from the last note of the verse melody, go up a major third to the first note of the chorus. (eg: C to E). Notice I said note, not chord. 
 
Step two : tap a rhythm on your knee or on your desk - a rhythm that is dramatically different from the rhythm of the verse melody. Try several different rhythms, - don't stop with the first thing that pops into your head. Record everything. You never know what'll come up and you may not remember some of the good stuff. 
 
Step three : once you have a rhythm that you like that is unexpected, starting on the note a major third up from the last note of the verse, add individual notes to create a short chorus. Make sure you repeat your chorus's first line somewhere in the body of that section. Beginners will write lines one and three the same, two and four the same, but you can write your choruses however you like. Be sure you don't simplify the process too much, and write predictably. And be careful not to borrow someone else's melody. 
 
Step four : test your chorus with your verse. Is it surprisingly different? Or is it too similar? Could you tweak it a little? Change even one note? Remove two? Vary a rhythm pattern? Record everything and put your files aside for a day or two. Then listen again. If your new "melody" makes it through the night, chances are it's right. And although it's "just a nursery rhyme", you'll have very deliberately constructed a note-by-note melody with a strong hook. When you're 100% happy with it, THEN add the chords and the track.