Organizing models/domain logic in a Rails app using Domain Driven Design [closed]

Question

I've been reading up on Domain Driven Design (DDD) and am a little lost on the implementation details. I like the philosophies that I've learned so far. For example, I've seen a lot of code make its way into ActiveRecord "models" that doesn't really belong there because of the "fat models" mentality. I think it makes a lot of sense to split up the real "domain/business logic" from the persistence logic, but what is a sensible approach to doing this in a Rails project? Should you put everything in the models directory? Should you only put DB/ActiveRecord objects in the models directory? Should you move everything out of the models directory to better organize in a lib directory? Any advice on this topic would be appreciated.