There is so much old data out there about debugging in Ruby that I wanted to post a quick reminder here so I could remember the current way to do it.

So here goes... debugging in Ruby 1.9 on Rails:

In the Gemfile...
gem 'debugger', group: [:development, :test]

Then from anywhere in your code:
debugger

One quick tip as well, type in irb from the debug console to get to a Rails console. Niiice!

Found the answer on Stack Overflow.