1. Start with soft butter. If the recipe calls for room-temperature butter, it should be soft but not runny. You can soften it for a few seconds in a microwave oven or let it stand in a warm place, such as near the preheating oven.
2. Measure dry ingredients accurately. Instead of scooping the measuring cup through the flour, gently spoon the flour into the cup, without shaking or packing the flour down. Then level off the top of the cup with a metal spatula or knife. Brown sugar is the exception to this rule; pack it firmly into the cup with your fingers until it is even with the rim.
3. Use a mixer. Unless otherwise directed by the recipe, beat the butter and sugar at a high speed (use the paddle attachment on a standing mixer) to blend into a light, creamy mixture. Beat in the eggs and/or other liquid ingredients until the mixture is smooth and homogeneous, then lower the speed or switch to a sturdy wooden spoon to incorporate the flour.
4. Chill the dough. If the recipe directs you to chill the dough so it can be rolled or shaped without sticking to your hands or the counter, but your kitchen is warm, you may need to refrigerate the dough longer than the recipe suggests. The dough should feel cold and firm but still pliable. If it becomes sticky as you work, return it to the refrigerator to firm up again.
5. Preheat your oven and check its accuracy. Turn it on at least 20 minutes before you plan to bake your cookies. Oven temperatures and heating cycles vary a great deal, so it is a good idea to check yours periodically with an oven thermometer on the middle rack to make sure it's baking at the temperature you set it for. Minimize opening and closing the oven door during baking to avoid lowering the temperature.
6. Try cooking parchment. This paper is sold in rolls or sheets in well-stocked grocery stores and baking-supply shops. Advantages: cookies won't stick, baking sheets stay clean, and you can use the same piece of parchment for several batches of cookies.
7. Use cool baking sheets. Never put cookie dough on warm pans. To cool pans quickly, rinse with cold water; dry before using them again. Choose shiny, light-colored baking sheets; dark-colored ones retain heat and tend to burn the bottoms of cookies.
8. Rotate pans halfway through baking time. Cookies will bake more evenly if they spend equal time on the top and bottom racks of the oven.
9. Store cooled cookies airtight. Most cookies will retain their flavor and texture for several days. Store cookies at room temperature unless recipe directs otherwise. Resealable plastic bags or airtight storage containers are ideal. Store different kinds of cookies separately, to prevent the moisture from softer cookies from affecting crisper cookies. Separate moist or delicate cookies with layers of waxed paper.
10. Freeze for longer storage. Most cookie dough can be frozen for several months. Thaw the dough in the refrigerator before shaping and baking. Most baked cookies can also be frozen if wrapped airtight to prevent ice crystals and freezer burn. The cookies will thaw quickly at room temperature.