Simply choose the bookmark icon on any post or forum to make it a Favorite. You can mark an item your Favorite wherever you see the bookmark icon:
On the Menu
On a Forum Post
Under the Banner
You can find all your Favorites in one place – My Stuff.
Under My Posts, you’ll find Posts you’ve marked as favorites, Posts from your favorite forums, and your favorite forums.
Under My Ideas, you’ll find Ideas you’ve marked as favorites, Ideas from your favorite forums, and your favorite Ideas.
Under My Favorites, you’ll find a summary of your favorite Ideas and Posts. You’ll see the recent posts from your favorite forums and idea labs, a list of your favorite forums and idea labs, and your favorite posts and ideas.