🚀 go-pugleaf

That's a pretty tall order! In my experience, the first step in 
creating an index is to create the list of keywords. This is a job 
which can't be automated unless you can somehow tell a script which 
words to ignore. I've usually exported the whole text and opened it 
in Word, because there are a lot of useful scripts about which will 
then generate a list of unique words in the document. (Perhaps 
someone will be along with a reference to one for Indesign.) This 
you (or the author, if that's not you) will have to go through this 
list word by word, deleting the ones that are not to be indexed. You 
have to be aware of capitalization, too, to avoid registering every 
instance of, say, 'street' while retaining those that refer to a 
place called Street. There are other things to watch for, too, like 
word variants (plurals, possessives and so on).
Once your word list is complete, you can use a script like Marc 
Autret's indexbrutal ( 
http://marcautret.free.fr/geek/indd/indexbrut/ ) to find each 
instance of your keywords and put the references in your index. It 
will then have to be checked again visually, so it's a long and 
tedious process.
-- 
Noel