Check whether the zipper slider is loose or worn
Align both sides of the zipper teeth evenly
Use pliers to gently squeeze the slider if it is too wide
Slide the zipper up and down to test the grip
If the teeth are misaligned, realign them before zipping
If the slider is damaged, replace it with a new one
Remove any fabric caught in the zipper
Lubricate the zipper lightly with wax, soap, or zipper lubricant
Sew a stopper at the end if the slider keeps coming off
Replace the entire zipper if the damage is severe