This hint is actually from my late mother-in-law. She never owned a dishwasher so this was a big deal to her and now is to me.
Instead of using a cookie sheet to bake frozen biscuits, or roast marshmallows, or reheat pizza, etc., use a doubled sheet of foil!!! Tear off the appropriate size, fold in half and spray with a cooking spray to prevent sticking.
The cooking time will be reduced and no clean up! It will save energy AND water AND washing soap and TIME!
Her motto: Why use a pan when a piece of foil will do?