If your Zipper is continually sticking, run a bar of soap up and down the "teeth". This will create an easy lubricant that won't hurt the fabric of the clothing piece.
Always Open Pants Zipper:
Worse than a sticky zipper is one that seems to "Fall" open and never stay up! If you're zipper won't stay up on your pants, here's an easy fix to get you through the night (while still managing to wear your favorite jeans!)
Loop a girl's hair tie to the top of the zipper slider, pushing one end of the hair tie through the loop of the handle used to close the zipper.
Then Feed one end of the tie through the other end and pull, creating a loop with the hair tie. Use the open ended loop to Attach the top of the zipper to the pants button.