I had been trying to find a way to add all of my Contacts, Groups, etc. from our company's Global Address List (GAL) to my local Outlook Contacts. That way, whenever I would need to send an email it would be easy to resolve/add everyone's name in the "To:" line. I finally achieved this by completing the following steps:
1. Open Outlook 2010.
2. Click "New" to open a new email.
3. Click "Address Book".
4. Select "Global Address List" in the dropdown list under the Address Book heading.
5. Click the first entry and hold down the Shift button.
6. Scroll to the bottom of your GAL and select the last entry.
7. Finally, right-click anywhere in the entries list and select "Add to Contacts". Depending on the number of Contacts in your GAL, this may take a minute or two.
Then, you're all set. The GAL has been added to your Contacts in Outlook. You can now easily begin typing a person's name, group, whatever and you will be able to quickly add exactly who you need to the email. Enjoy!