Return to the Moon

The Apollo equipment has sat abandoned on the lunar surface for over 40 years. Now there is a renewed excitement and drive to return to the moon. This time, not to just plant a flag, but to colonize. How would we accomplish this? And why would we do it?
The race is on to colonize the Moon, to uncover its hidden riches and discover if humanity can really survive on another world. The Moon is our gateway to our solar system, it's the stepping stone we have to become a multi-planetary species.