Thanks to advances in the production of flour, it's no longer necessary to sift flour for most recipes. However, measuring flour accurately is critical to the success of your cookies. Always measure flour with nested metal or plastic cups. Glass or plastic cups with graduated measurements on the sides and spouts are meant for liquids. If you use a liquid measuring cup for flour, you could end up with an extra tablespoon or more per cup. Begin by stirring the flour while it is still in the storage container. Using a large spoon, gently spoon the flour into the measuring cup and level off the top with the straight edge of a metal spatula. Do not pack the flour into the cup or tap it to level it.