I have visitors coming into town this week. So I gave them the advice I give everyone who visits: The Metro is easy. The hardest part is buying your ticket. But, if you want to make it past the escalator alive, stand right, walk left. Most people laugh this off. But they learn.
Since I've gotten here, I have been thrilled with the system, which is strictly enforced with impatient sighs and exCUSE me's from angry commuters who have been looking for the first excuse to release their hatred of life that day.