A medium size Lemon yields 2 to 3 tbsp. juice and 2 tsp. grated peel.  Reeze the juice in ice cube trays, then store the cubes in plastic bags to use as needed.  Pell can also be wrapped and frozen for later use. 

To extract the most juice, bring refigerated lemons to room temperature and and roll firmly on a flat surface using the palm of your hand.  Or Microwave a whole lemon on high for 30 sec, then roll.