How To Update Table of Contents in Adobe InDesign
You probably already know that InDesign allows you to update table of contents. This means that after changing some header, order of pages and so on, you can update existing table of contents without to delete and recreate it.
Now, if you try to update table of contents from Layout menu, this option is grayed out by default? The problem is because InDesign does not know what you want to do and option Update Table of Contents is grayed out, for good, because if this option is available pressing it without to select table of content first, wont make any changes and user may think: this option is not working. Option works and works very good but you need to select table of contents first using Selection Tool or to click inside it to appear blinking cursor with Type Tool active. After selecting table of contents or clicking inside it with Type Tool go to Layout > Update Table of Contents to update any changes in document related to it.
InDesign / Creating a table of contents
Product used in this tip: Adobe InDesign CS6