Gently pull the zipper slider back and forth a little
Check for fabric caught in the teeth
Pull the fabric away while easing the slider
Rub a graphite pencil tip on the teeth
Apply a small amount of soap, wax, or lip balm to the teeth
Use tweezers to remove any trapped threads
Straighten bent zipper teeth with pliers
Hold the zipper tape taut while moving the slider
Do not force the zipper
Replace the zipper if it still will not move