It used to work by literally picking up anything you saw, links in chat, viewing a vendor's items for sale, a seller in the baz, etc. I would go to out-of-the-way vendors to see what they had to force it to update items when needed.
Now, it just never updates. I have new ToL items in my inventory, see new links in chat channels, etc. and it never picks them up. I have to wait on someone else to get them into the DB. When I zone or log in, the IC will scroll through items I possess, but I can't make any logic out of what it views and why. It likes to miss things.