In this video 'Boxtape' gives some great advice about writing the 'bridge' to your song, and lets us see her approach to song-writing and editing.
The main purpose of the bridge is to provide contrast to the previous sections of the song, and it's a good idea to do this lyrically, as well as musically.
One common technique for writing a bridge is to shift the perspective, or approach the story from a different angle.
You could try changing the narrative perspective (who is telling the story)
Change the time perspective (tense) - for example if your song is written in present tense, your bridge could be looking back at it from the future.
Another technique for quickly developing an effective bridge is to 'do the opposite' from what you're doing in the verses and choruses.
LUCKY - BRITNEY SPEARS
SAFETY NET - ARIANA GRANDE
BUTTERFLY - DEMI LOVATO
ASTRONOMY - CONAN GREY
Once you've written your chorus and your verses, both you and the audience should have a really clear idea of what your song is about. All that is left to do is to add a bridge to create some interest.
Try to think of a different perspective on the story you've told. How would your narrator feel about the story if they looked back on it from some point in the future? How would another character in the story feel about the situation? If you need to, repeat the 'destination write' from the previous lesson, but this time from a different point of view.
Once you've decided on what your fresh perspective is going to be, write a four-line bridge.