Devise User Follow System
From what I remember Michael Hartl's Ruby on Rails Tutorial does a very good step by step guide to the following/followed via ajax part.
Thanks John! I've just read the recommened book/chapter and I think I get it. Still would be cool to get a video tutorial though.
Michael Hartl does a video Tutorial via the Learn Enough site, you need to subscribe though. It's good but its everything thats in the book.