When you tag a topic, you creat a 'forum'. Tag something and go to "My Tags". Now, your tag will be there and you can immediately go to all the threads on which you have tagged.
I try to keep mine general, like 'cats', 'spiders', 'community, etc. If you get to specific, like 'so and so is an idiot', you are going to have so many tags they become useless. Kind of like a yellow ribbon on the tree with the stash of gold buried below, and someone puts a yellow ribbon on every tree.