Align the zipper teeth
Move the slider to the bottom
Gently wiggle the slider back onto the teeth
Pull the fabric away from the zipper path
Use pliers to slightly pinch the slider if it is loose
Use a pencil, soap, or wax to lubricate the teeth
Remove any caught fabric or thread
Zip up slowly and evenly
Replace the zipper slider if it is damaged
Replace the zipper if the teeth are broken or missing