Joomla 2.5 Template (theme) development

I need to develop a Joomla template for version 2.5.  I created a site a few years back using Joomla 1.0.15 and cheated a bit as I was short on time, I took a template that had been developed by someone else and tweaked it to make it work with my design.

This time I’m doing it from scratch as I really like to know how these things work.  I have read various blogs and posts to get some ideas and hints and looked at the structure of an existing template, the very basic structure of the template looks like this: