Hi Dirkstar,
You can check the box at the bottom of the page of any thread you want to be notified for. But there is no way to be notified for every thread, in particular new thread that you can't mark in advance, obviously.
The most convenient way to follow ALL new posts on the forum is to use the following link:
http://poiscenter.com/forums/index.php/action=recent.
That's what I use.
( it is more efficient than the RSS feed, which has only a five posts span, and if there have been more than 5 posts since your last visit, you will miss those over 5 )