Begin each batch with a cool cookie sheet to prevent the cookies from spreading too much.
Arrange the dough on the cookie sheet with enough space between each cookie, as directed in the recipe, to allow for spreading as the cookies bake. Place the cookie sheet on a rack in the center of the oven, leaving space on all sides for air circulation.
In a conventional oven, its best to bake just one sheet at a time. If you must do two at once, swap shelves and rotate trays halfway through the baking time. In a convection oven, which uses a fan to circulate air, you can bake several sheets at once. Convection baking will reduce baking time by several minutes; watch the cookies closely until you are sure how long to bake them.