Know your baking sheets. Do cookies brown more quickly on one? Do cookies tend to stick on another sheet?
Parchment paper can be a big help. It stops cookies from sticking to pans and makes for much easier clean up.
If baking two trays of cookies at the same time on different racks, be sure to rotate them halfway through baking.
Allow baking sheets to cool completely between batches. Don’t put dough on the sheet until it is cool to the touch.
Make sure your ingredients are fresh. If you bake only once a year, you should buy new baking soda and baking powder.