How do I change a username? (shortname and home folder) Under Linux, this would be a no brainer. Just go into /etc/password and edit that, and rename the directory in /home. 
I want the new shortname and the new home folder to match after the change.
Apple's own instructions work quite well. There may be more complex and faster ways out there, but I've never run into an issue (such as incorrect permissions) with these steps.

Mac OS X v10.6 and earlier: How to change user account name or home directory name