They put up an information wall: they share nothing in advance of the product launch, restrict access to the launch events, restrict livestreams from the events, ignore social media around the events and let the community speculate and fester ad nauseum. The fanboys flock to the liveblogs, congregating around the event as it happens, just as Microsoft and Apple hoped they would.
What does Google do when they want us to talk about the Nexus 4 going on sale?
They make the launch a tease to end all teases.
They announce a launch date but no launch time.
The die hard geeks stay up until midnight to order the new phone at the first available moment, only to discover that it isn't yet available in the US. Hour after hour the geeks refresh the Google Play store, but they leave frustrated and excited. While they are waiting and watching, the phone sells out in country after country around the world, often in a matter of minutes.
As of this writing there over 350 comments on The Verge discussing this very question: when will it be available?
Nobody seems to know. But thanks to Google, we're here talking about it.