Rails MVC: How to deal with fat models

My presentation on the last DRUG (Wroclaw Ruby User Group, D stands for Dolnoslaskie) about Rails fat models.
I covered some of the techniques we use in our projects:

• current_user is never nil
• a class for each user type - User, Guest, Admin, SuperAdmin, Partner
• remove "if" statements from views
• minimize the number of "if" statements in controllers and models
• modules to extract common behavior from models
• one controller action calls only one model method
• in controllers everything goes through current_user
• using custom exceptions for Model - Controller communication

Rails MVC: How to write models on Prezi