Jim is exactly right. First go to a forum that interests you, subscribe to the forum under forum tools. Whenever u find a thread that u have interest in, simply do the same thing and go to forum thread and subscribe to that thread only.
A smart idea would be to go to the main forum first. Pick out the forums that u like, press the link and one by one go to forum tools and subscribe to each forum. After that, follow my example of subscribing only to threads that interest u. Each time a thread comes up in a forum u are interested in, simply open that thread and go to forum tools and subscribe only to that particular thread. At the top of the thread it will ask you if you want to go to view first unread. If that thread or forum no longer holds your interests just unsubscribe individually, and you wont get any notifications of that thread or forum.
This does not require being a rocket scientist. Anytime u have a question feel free to ask.