Go to the bottom of the stairs. Position the nose of the pliers under the bottom edge of the carpeting and clamp the pliers shut on the bottom edge. Pull up until the bottom stair's carpeting is pulled up.
Put on heavy utility gloves, and grasp the loose bottom of the carpeting. Carefully pull up the carpeting moving up the stairs as you move along.
Pry up tacks and staples as you encounter them using either the pliers or the tip of a flat-head screwdriver. Depending on your carpet installation, you may or may not encounter staples and tacks during the carpet removal.
Inspect the stairs after the carpet is removed and the runner pad that may remain. Use the flat-head screwdriver or pliers to remove tacks and staples holding the runner pad in place. Note that many installations will have a separate piece of carpet pad to remove for each stair.
Stick the end of a prybar behind each tackless strip revealed after removing the runner padding. Pry up each tackless strip. If needed, tap the prybar lightly with a hammer to get better leverage and a tighter grip.