Lets talk about preparation.
Think of baking as a science project, if you start mixing and have to run to the store to get something you forgot the whole process is interrupted, make sure you are prepared to finish the process once you've started. 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.