Lift the stopper to the open position
Look for a hidden set screw on the side or underside
Turn the stopper counterclockwise to unscrew it
Pull the stopper straight up if it is a push-pull type
Twist and lift the stopper if it is a toe-touch type
Remove the overflow plate screws and pull the linkage out if it is a trip-lever type
Use pliers wrapped in a cloth if the stopper is stuck
Apply penetrating oil if corrosion is holding it in place
Clean the drain threads after removal
Replace the stopper with the same type and size