Accuracy in measuring ingredients is critical to successful cookie baking.
Flour. Stir the flour in the bag or canister to lighten it. Gently spoon flour into a dry measuring cup. Level it off the top with the straight side of a knife.
Granulated sugar. Spoon the sugar into a dry measuring cup. Level it off the top with the straight side of a knife.
Powdered sugar. Sift powdered sugar before measuring. Spoon into a dry measuring cup and level off the top.
Brown sugar. Spoon brown sugar into a measuring cup, packing it down with your hand or the back of a spoon as you add more; level off the top. When the measuring cup is turned over to remove the sugar, the packed brown sugar should hold its shape.
Butter or shortening. To measure sticks of butter or shortening, follow the markings on the wrapper. To measure unwrapped butter, soften it, and then use a rubber spatula to firmly press the butter into a dry measuring cup, removing any air bubbles. Level off the top with the straight edge of a knife. Measure shortening from cans the same way, except do not soften.
Liquids. Pour the liquid into a glass or clear plastic liquid measuring cup set on a level surface. Bend down so your eye is level with the marking on the cup.