If you're using Cocoa and you're not using the the NSDocument - well things should be pretty straight forward when you look at the example programs.
On the other hand, if you're trying to figure out how to do an NSDocument based app, things are a little more complicated for the beginner. All of the Objective-C books will say wonderful things like "Open Project Builder and select 'Cocoa Document-based Application'".
Unfortunately (or fortunately - depending on your p.o.v) we don't get that in PyObjC land. Actually - you do get a template with PyObjC, but we're not going to use it.
So in the grand tradition of all code that falls into the category of "almost useless sample code i found on the internet that only covers a trivial example" - here's a quicky look at a port of Hillegass's "RaiseMan" application - and building it up from scratch.