Use a light-colored baking sheet, use a silicone baking mat, or line your cookie sheets with parchment paper. It is also important not to cook your cookies on the bottom rack; you want them in the middle of the oven for even baking. (So, for the best results, bake only one cookie sheet at a time.) Another good tip is to let your baking sheets cool in between batches of cookies. (When the weather is cold, I just put my cookie sheets outside in between batches, lol.) Lastly, I recommend setting your timer for a minute or two before the recommended baking time and checking your cookies for doneness.