Another way is to click "Settings" in the upper right corner of the page. That takes you to a list of threads you are subscribed to, and that have posts that you haven't read. When you post in or start a thread, you are automatically subscribed to it. You can also subscribe to a thread without posting by clicking "Thread tools." If you want to remove threads from this list, just click "Unsubscribe" near the title of the thread. Using Settings is a great way to keep track of activity in threads that you have a specific interest in.