Something to keep in mind is that you should reduce baking temperature by 25 degrees and check the food often as it may be ready up to ten minutes earlier if you are substituting a glass dish for a metal baking pan. This is because glass doesn't heat up as quickly as metal but will become very hot once heated up.

Position the rack in the lower third (just below center) of the oven. If baking more than one pan on the rack, rotate the pans from the front to the back a little over halfway through the baking time.

For more even baking, position oven rack at the center of the oven and bake one sheet of cookies at a time. If you prefer to bake two sheets, space racks so oven is divided into thirds and switch cookie sheets top to bottom and back to front halfway through baking.