Once you've logged in, go to "My Account" (it's on top box on the left). From that page, click on "Watched Forums" (at the top). Then check the boxes of those Forums you wish to receive in your e-mail (I have them all checked so I don't miss anything), and then click "Save" on the bottom right.
Although the information posted by Maria is correct, it is only limited to the members of the AGG that have viewing access to all forums and topics.
There is a group of AGG Discussion Board members that can not simply adjust the watched forums as suggested.
The solution is for an administrator to personally change the viewing option of each member to see any new forum added.
I would also like to add that some posting from the Directors Corner, which was originally setup to be a private message area between the directors are being view by many other Discussion Board members.
You may want to check into this or limit your use of this area if you want these messages to be private.