Metrics to pay attention to

What are the most important sales metrics you should take the time to analyze on a weekly/monthly/quarterly basis?

For me the most important metrics are time & effort spent per customer/prospect. This includes time spent on the phone/in meetings; how many tries till you reach them etc etc; Source of the lead is also quite important in my opinion, you want to know how different channels perform against each other. And then, of course, the conversion rate is also essential.