Using these tags in your HTML (XHTML actually) is quite easy. For example, to print to the blog's title, you'd use this:
<data:blog.title/>Notice the / before the >. That's needed because templates are XML so all tags have to be closed. If a data tag has to go inside another tag, the syntax is a little different. For example, to enclose the title in a link to the blog, you'd do this:
<a expr:href="data:blog.url"><data:blog.title/></a>Notice the
href. That tells the template engine that the value of this attribute is an expression to be expanded. I don't know the details, but that's what I've understood from it.
<![CDATA[ ]]>tags so that I don't have to worry about escaping quotes and relational operators. However, this also means that any data tags I used would be treated as plain text and ignored. I searched for docs on how to do this, and there was none.
I then went to the Edit Template section, and clicked the checkbox that said "Expand Widget Templates" and then searched through the template code for other <script> tags. I found some, and got my answer from there, and this is what my delicious call became:
Pretty simple, but it took me a really long time to find any documentation on the subject. Let this blog post serve as documentation for anyone else who needs to do the same.