I have "Automatically subscribe to posted threads" or whatever checked in my user settings. This way, whenever I post in a thread, if someone else posts, then I hear about it.

I never thought to use it as a way to remember threads with useful information in them. I figure, if you subscribe to every useful thread, you have to spend just as much time looking for the one you need as you could by searching the forums. But thats just my personal usage theory.