Mark Levison wrote up and introductory article on Kanban for InfoQ. It's from a people perspective and worth a read if your new to this scene or interested. I'm especially happy he conveyed the "work to done" concept.

For me that's the biggest thing. Done has a pretty simple definition: "it's in production." I think this is a message that should be in the forefront. As with any message, repetition is key.

Throughput accounting (David Anderson's book on Agile Management, great intro) is a big, big, big deal. This is the theory/justification/whatever of the done definition.

The other thing that's really important to me is the visual management stuff. You can see where things are getting bogged down. Corey Ladas pegged this best in his leading indicators post. Queue utilization trumps velocity/cycle time in having an effect on throughput.

Standard work and thinking about your pipeline is rather critical. Continuous improvement happens much more regularly when we say "hey, here's how we're gonna work" and make that explicit with a whiteboard, cards, and a marker, and tweak over time. There's gotta be a baseline.

Other things, like cycle time, seem less important (but still matter) as, in the case of cycle time, it's just a re-imagining/slight reconfiguration of an agile concept (velocity). Of course it's important to establish it and improve upon it, but I don't necessarily see it as new ground.