A cool feature of Movable Type is the ability to use alternate templates for the MT application itself. Instead of hacking MT's default application templates directly, you can create a directory for alternate templates (in the same directory where mt.cgi resides), configure the path in mt.cfg, then upload your hacked/tweaked templates for MT to find there.
In mt.cfg add the following:
AltTemplatePath ./tmplx
(You can name your Alternate Templates folder whatever you like. I use /tmplx so the folder will reside directly beneath /tmpl when I'm accessing it via FTP.)
