I understand I can send an SMS or email to a contact, but I can't figure out how to ask for directions to the contact. Is there a voice command for Google Now that will pull up directions to a contact's address? If so, what happens if the contact has more than one address?
If there isn't a way to do this currently, is there a shortcut to pull up the Contact record, where I can click to the map?
This feature isn't available as of now. But you should frequently check the Google Now app page for such updates. This feature is available on Siri though, but that's probably irrelevant right now. In the meantime, you can still get turn by turn navigation to take you home by saying " directions to home". It'd be a good app feature though.
you can search for a contact by saying "open contact" then the person's name. Takes it a few seconds but it shows name numbers and addresses. All of which allow you to tap to call, text or get directions directly from Google Now.
Google now is an extension of the search function, so you could use the search voice function to issue a navigate command. However due to my accent I find that it causes issues.
However you can navigate directly to a person via the contact app. when the contact app is open, search for contact you want (you need to be in the contact tab, not the phone tab - favourites tab will work too). Press on the person's picture (or icon if no picture) - this will pop up an action bar of everything you can do with the contact, from phoning, e-mailing, facebook etc, and if you have an address for that person, by scrolling the action bar you should see the map icon, which if pressed provides their address in the action box. Press the address, choose maps if it isn't already your always use. If you have navigation set up to be your standard on the bubble bar press the navigation option, otherwise press on the bubble bar to bring up the address, and choose the navigation option. If directions only option, use that and when directions shows details to get there, use the navigation button on bottom right to go into it.