If you're running batteries don't use a 78XX line regulator. They're not the most efficient.
Look for a switching regulator. I'm not quite sure which one everyone here likes to use, but there does seem to be a few favored ones. If you can't get your hands on it, the 78XX line of regulators have copious amounts of circuits online to follow if you just Google, but iirc you just need filtering caps of like .1uF on the input and output. Just make sure your voltage rating on your cap is higher than the voltage that it's filtering.