You can click on the Watched Topic icon in your array of mini-icons at the top right of every screen. This will display a list showing all your watched topics along with indicators to show if new posts have been added to the topic. You can remove topics from the list by checking them and clicking the Stop Watching button.
The forum will automatically send you one email when someone posts to a topic that you are watching. No further emails will be sent until you visit the forum again. This will prevent you from receiving too many emails which would happen otherwise if you were watching several popular topics.