Pinch the edges of the carpet along the wall with a pair of pliers and pull the carpet up off the tack strip nails. Grab the loose carpet with a free hand and pull up. Each time the carpet gets hard to pull up, use the pliers to pull the edge up. Continue this process until you have pulled the carpet up and down the stairs.
Strike the carpet with a hammer to break it away from areas where staples were used to hold it in place. Staples are usually found beneath the edge of a step and the face of the vertical riser. If the hammer doesn't work, then use the pliers to pull out the staples. You can also use a flathead screwdriver, sliding the head underneath each staple head and then prying up. The prying will lift the staple up and out.
Pull up the pad. Staples holding it in place will tear through the pad and remain in the floor. Use the pliers or screwdriver to remove them. Roll up the pad and carpet and discard. Keep the staples together and also discard.
Slide the flat edge of the pry bar blade up to the edge of the tack stripping. Strike the end of the pry bar with a hammer to get it to slide under the tack strip. Pry down on the bar to get the nail holding the tack strip to the stair to lift up. Remove the tack strips and throw them away.