OK, here's a quick and dirty explanation of how OS X creates new user directories.
OS X uses a template for all new accounts based on the info in this directory:
/System/Library/UserTemplate/English.lproj
It contains all the directories and files that appear by default for a user, including all of their preferences.
Here's more info on the topic:
http://www.stat.ucla.edu/esources/deployment/notes.php
Be sure to make a backup copy of the template before you start working.