What's the easiest way to get contact info from gmail into Mac's Address Book?

This may be broader than what you are looking for, but in gmail you can go to Contacts -> More -> Export and make sure you select vCard Format.
Then just open the file that downloads to your computer and it should add the contacts to your address book!
step 1: get to contacts
Step 2: click more and then export
Step 3: make sure you select the vCard option, then click Export!