At the top of the forum area, to the right of your avatar and "Logged in as...", there are a couple of nifty buttons: Watching and Subscribed. Clicking these will show you the topics you have selected to Watch or have Subscribed to using the Watch or Subscribe buttons at the bottom of the page (right above the stats area).

If you want to receive email alerts when a topic has been replied to, then Subscribe to it. If you just want to keep track of certain topics and don't want to receive email alerts, then Watch them instead.

You may feel a temporary counter-intuitiveness regarding this feature: once you've Watched or Subscribed to a topic, the number in the Watching and Subscribed queue/button doesn't immediately increment. It's not supposed to, as it is not counting the number of topics Subscribed/Watched. It is counting the number of replies that have been made by users other than yourselves on the topics Subscribed/Watched. And there is a 5 minute refresh offset, meaning if you Watch a topic, then somebody immediately replies to it, you won't see the 0 turn into a 1 until you have refreshed/returned to the page 5 minutes later.

Hope that makes sense. It's supposed to be useful.