For headings, use heading tags: h1, h2, h3, h4, h5, h6

<h1>Title<h1>
<h2>Subtitle<h2>
<h3>Chapter title<h3>
<h4>Scene title<h4>
<h5>Subtitle<h5>
<h6>Footnote title<h6>

For emphasis, use emphasis tags em, strong

<em>Rodney</em> McKay
I will <strong>never</strong> understand you!

To quote poetry, phrases or titles use quote tags: blockquote, q, cite

<blockquote>
To quote a block of text
</blockquote>
Use q to <q>To quote a phrase</q>
Try cite to cite <cite>a phrase or title</cite>