For all drain stoppers, removal generally requires that the stopper be placed into the open position and then pulled straight upward. Bathtub pop-up drain stoppers have several methods for removal depending on whether there is a rocker arm attached to the base of the stopper.
To place a pop-up stopper in the open position, check the top of the stopper for a trip lever. If a trip lever is present, flip it upward to open the stopper. If there is no trip lever, rotate the overflow faceplate until the stopper opens.
Pull the pop-up stopper upward to remove it from the drain. If the stopper is difficult to pull, wiggle it in place while pulling it upward. Some stoppers have a horizontal rocker arm at the base to help hold them in place. If the bottom of the stopper clears the drain opening but a rocker arm is visible, pull the stopper horizontally to remove the rocker arm from the drain.
As the rocker arm can scratch the bathtub surface, spreading a piece of cloth along the bottom around the drain helps prevent damage. PlumbingSupply.com also recommends keeping a bucket on hand for the messy debris that comes out with the stopper.