If there are favourite threads you want to keep track of, you can bookmark 'em to keep 'em all in one place.
Click 'ADD BOOKMARK' inside the thread/topic you want to bookmark.
It will appear in your bookmarks list accessible via top menu's 'My Bookmarks
Alternatively, you can subscribe to your favourite threads
/or whole boards/ via 'NOTIFY' button (found right next to 'REPLY' button, or next to 'NEW TOPIC' button, in case of subscribing to a whole board).
Possible advantage of notifications over bookmarks is you get emailed or messaged when new replies are posted to your subscribed topics.
Your current notifications are found by clicking top menu's 'Profile
' button and choosing 'Notifications'.