Here on TV Tropes, we make a life out of categorizing tropes and stuff. For this purpose, we have a whole lot of indexes where we can add pages on so that they are categorized. Putting something on an index is also known as "Indexing".
How do I add something to an index?: Just add a working link to the page you want to index after a bullet in the bulleted list on the index. The page you want to index has to exist already, by the way - otherwise, you'll have to re-edit the index page for the page to display on the index.
How do I turn a page into an index?: This is done on the Tools menu on the left side of the page. There is a button labeled "Set Page Type." Setting it to "Index" or checking the "index" box turn the page into an index. You'll probably have to edit the index page afterwards for the indexing to kick in.
I added something to an index/turned a page into an index, but it's not working: First, always make a blank edit on the problematic index page. If that doesn't work, check that the link(s) you added are working links and that you've set the page type of the index correctly.
How do I make it so that only certain parts of a bulleted list in an indexing page are part of the index?: Put the [[index]] markup before the first bullet in a list that should act as an index and [[/index]] after the last bullet that should act as an index. You can do that several times on the same index page.
The index is indexing pages that shouldn't be indexed: Most commonly, it happens when a bullet in the index contains a paragraph break (the first bluelink after the paragraph break is registered as a new bullet) or if there are redlinks after.
How do I move an index?: Like any other page, but you need to change the page type to no longer index before.
A redirect is creating an index bar: The consequence of not changing the page type before redirecting; break the redirect and change the page type to something like "subpage", then restore the redirect.
Out of curiosity, how does the indexing mechanism work, technically?: When an index page is saved, the system looks though the page and extracts all the line items (all the lines that start with an asterisk). It goes through those lines and extracts the first link to a wiki page on that line. After this process goes through all the line items, we have a list of page titles in the order given on the index page. This is the index. We save it with the title of the index page and build that blue nav-bar from it and display it when the page is viewed.
What are the markup bits that look like <<|Administrivia|>> at the bottom of a page?: These are artifacts from the old indexing system. Feel free to remove them.