You can subscribe to any thread, just click on Thread Tools
in the header in the thread you want,
then on Subscribe to this Thread, and choose if you want an email notification.
You can choose instant, daily, weekly, or no notification!
To find your subscriptions easily, just click on the Quick Links drop-down menu under
the Welcome box, click on Subscribed threads, and it
will take you to your list of Subscribed threads.
They also show in your User CP, but only the ones that have been recently replied to.