> In other words, how would an expert go about building a responsive [...] website I'd really like to know what I need to take a regular WWW 1.0 website (html 4.01 strict) and make it at least vaguely responsive to mobile screens.
Nothing, it's responsive by default if it's just text and links. Mobile browsers will reflow it. Once you start bringing in divs, widths is when it becomes not responsive.