I originally used py2deb and it created my rules file for me that I now just manually edit, and I decided I wanted more control. When you are ready to package your program you create a specific filesystem structure.

I recommend grabbing py2deb, building an initial package with it, then copy the directory structure somewhere for you to edit and maintain as you go. It will create all these files below for you in the proper formats, then editing them is easier (vice creating them by hand).

Once this structure is properly in place, you simply run:
From yourapp-1.0 directory and it will create your deb file for you that you can install on the N900. Once it runs and installs (and removes) successfully on your N900, you can follow the procedures at the Extras Assistant to building your source tarball and upload it to the repositories.

Some places to start:
Here, here, Here, Here

As far as what I mean by "Maemo-ized", when you run a PyQt4 app in a normal Desktop things such as QDialog and Popup boxes are actual message boxes, squares with buttons on the screen. They are rollup windows in Maemo. Also, the background and all the colors go to black, whereas on a desktop they will be white by default. Menu's can look different on a desktop than in Maemo, etc.