Well, there are a few different ways to debug your app. What are you
trying to find out?
In the model you can put:
class ModelName < ActiveRecord::Base
That will give you the call stack everytime the model is hit.
If you want to debug params within your views you can place:
<%= debug params %>
Which will list all of the params in your views...
The list goes on and on..
What do you need to check?