Off-page elements
Link text
<a href="url">some link text</a>
This is one of the two most important elements for good rankings. The link text can be on pages within the site or on other sites' pages. Either way, it is important. The target page's main search term should be included in the link text. When possible, don't use identical link text for every link that links to a page, but do include the target page's main search term in the link text.
Google attributes link text to the target page - as actually being on the target page, and it treats it's pseudo-presence as being an important element of the target page. Links carry even more weight if the text around them is concerned with the target page's topic and search term(s).

On-page elements
The Title tag
<title>some title words</title>
This is second of the two most important elements for good rankings. Make sure that the page's search term is contained in this tag, and place it as near to the front as is reasonable, whilst ensuring that it reads well. There's nothing wrong with placing the search term up front on its own, followed by a period; e.g. "Pagerank. Google's PageRank and how to make the most of it". The target search term is, of course, "PageRank". Obviously each page's Title tag should be different to the Title tags on the site's other pages.
The Description tag
<meta name="description" content="a nice description">
Some search engines, such as Google, don't display the Description like they used to do but, even so, it should still be included in each page for those engines that do, and for the odd times when even Google displays it. Write an appealing description for the page and incorporate the page's search term into it at least once and, preferably, twice. Place one instance of it at the start or as near to the start as is reasonably possible.