Hi UncleCheese
Yes, either the <% require %> tag or just plain html includes. The require tag is possibly the better choice since it prevents duplicates.
From studying the SSViewer class, I was able to figure out how this tag works:
The first part is the keyword "require", followed by the method to call with arguments in braces.
<% require css(path/to/my/file.css) %>
Will call Requirements::css('path/to/my/file.css');
Same goes for JavaScript, eg.
<% require javascript(path/to/my/file.js) %>
HTH