When I'm baking, I often have at least three wire racks going at the same time:
• Wire Rack #1 is near the oven. Conveniently positioned to receive hot cookie sheets coming out of the oven.
• Hot Cookie Sheet #1 is placed on Wire Rack #1.
• Cookie Sheet #2 goes in oven. (Timer on...)
• Timer's almost done - move Cookie Sheet #1 to Wire Rack #2. Ding! Time to take out Cookie Sheet #2.
• Cookie Sheet #2 is placed on Wire Rack #1.
• Cookie Sheet #3 goes in oven. (Timer on...)
• Timer's almost done - transfer cookies from Cookie Sheet #1 to Wire Rack #3; move Cookie Sheet #2 to Wire Rack #2. Prepare Cookie Sheet #1 to go back to oven. Ding! Time to take out Cookie Sheet #3.
• Cookie Sheet #3 is placed on Wire Rack #1. Cookie Sheet #1 goes in oven.
• Repeat.
Juggle, juggle, juggle. As you can see, when I'm baking, I can run out of wire racks since the cookies are cooling on Wire Rack #3 and spilling onto Wire Rack #2. This is when keeping empty egg cartons come in handy. They are sturdy enough to hold a heavy tray of brownies as well as provide enough airflow for brownies/cookies to cool. If your kitchen looks anything like mine during the holidays, just keep a couple of those egg cartons you were going to throw away around for your bake-a-thon.
Bonus Tip: If your cookies are low, diagonally place a pair of egg cartons - on top of your cookie sheet on opposite corners. This way, you can stack a few trays, keeping precious counter space free. Now get baking!