Earlier this week I showed you how to access your Google Contacts from your iOS device. Here’s how to do it on your Mac (on Mac OS X Lion or Mac OS X Mountain Lion):
Go to the Apple menu > System Preferences > Mail,Contacts & Calendars > Add Other Account > Add a CardDAV account > Create.
Username: Your Gmail or Google Apps email address
Password: Your Gmail or Google Apps password
Server Address: google.com
If you already have your Google account listed on the left of the Mail, Contacts & Calendars panel you won’t see an additional item, your new CardDAV account will just be merged in with that account.