How to setup correctly an application with Python and Tkinter

I am a command line kind of programmer; GUI tools make me shiver and growl until I can scuttle back to the safety of a terminal. However, from time to time the need arises to create a functional — albeit simple — user interface, be it due to the target system or because the tool needs to be shared with less tech-savvy friends. In those rare cases my go-to choice of tools is usually…