Why do my cookies spread so much when baking?

I received a message from a friend last night in desperation trying to bake hundreds of cookies for her son's school that kept spreading.  After about two failed attempts in the oven she called.  Baking is SO sensitive! Here are some of the most common causes as to why your cookies may be spreading too much:
- Your dough is too warm and needs to be chilled
- The baking pans were greased - tip: don't grease baking pans unless the recipe calls for it
- The butter was too soft when using it in the batter.  At room temperature you should be able to poke an indentation with your finger but the indentation shouldn't stay
- You substituted shortening for butter
- The baking pan was warm when before you put it in the oven
- You used the wrong kind of flour.  Unbleached all purpose flour is the best for cookies.

Always bake a test batch when baking a large amount of cookies.  If the test cookie does not come out right you can then adjust before baking an entire batch.  Hope this helps! If anyone has any other baking questions.  Please feel free to ask!