You have lots of options for Nook Support Forums to notify you about changes and updates to content you care about. Changes to content you create and participated in are always followed in Inbox. You can also click "Follow" to bring updates about documents, discussions, and Place activity into an Activity stream. Following any item in Inbox pulls activity into your read-tracked Inbox stream, and you'll be alerted about it as soon as you log in. (Be sparing about what you follow there: you don't want important items to be buried in a sea of updates you don't care about.)
To begin following activity, navigate to the area you care about — a place or document or blog or person, for example — and click "Follow" under Actions. Then select one or more streams to follow it in. The button changes to say "Following." Click it again to stop following.
Whether you get notified by email about stuff you follow is up to you--just click Preferences under your name to decide whether to get email about everything you follow, just Inbox items, or some other selection of items. To enable email notifications on any stream, edit the stream and turn Email Updates on at the top of the page.