Valsad,
In this case, when someone writes "tag" in the thread, it just keeps the thread on the first page of the forum, it serves the same function as "ttt" (to the top) you see in the Classifieds. In order to follow a particular thread, open up the thread, look in the upper left corner for a small grey box that says "thread options", click on the grey box. A drop down menu appears, click on "follow thread". You then go to the "my stuff" menu and find "followed lists", click on "followed threads" and you're there. The forum seems to automatically add threads repeatedly opened, so it may already be there. Hope this helps.