Have plenty of all-purpose flour, granulated sugar, baking soda, etc. Have all your tools ready to use. See tools page for those you will need. You only have to grease the baking sheets when the recipe calls for it. So pay attention to the recipes.
Some cookies spread too much if the sheet is greased.
Wash and cool ungreased baking sheets between batches of cookies. For puffier cookies omit the brown sugar and use only granulated sugar. To tell if something is done insert a wire cake tester or wooden pick in cake s center. If it emerges perfectly clean, the cake is done. However, tests vary.