Link structure within the site

An obvious, but sometimes overlooked, aspect of search engine optimization is to make sure that search engine spiders can actually find (crawl) all of the site's pages. If they can't find them, they sure as hell won't get spidered and indexed, and no amount of search engine optimization on them will help.

The Title tag
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=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.

The Keywords tag [meta name=keywords content=keywords]
The words in the Keywords tag were never treated as keywords by the search engines; they were treated as text on the page. The tag isn't as effective as it used to be but there is no reason to leave it out. So put plenty of relevant keywords into the tag and include the search term once at the front, and a second time further along the line. There is no need to seperate keywords and keyphrases with commas, as is often done, since the engines ignore commas.

Text
Use the search term as often as you can on the page whilst not detracting from the page's readability. Make sure that you use the term once or twice very early in the page's body text and as often as possible throughout. Reword small parts, and even add sentences, to make sure that the search term is well represented in the text.

Alt text [img src=url alt=some alt text which is displayed on mouseover]
Include the search term in the alt text of all images on the page. Keep in mind that some systems such as Braille readers and speach synthesisers use the alt text, so you might want to make them usable whilst including the search term.

Summary
Select your main search terms.
Allocate each search term to a suitable existing page. Split some pages if necessary. Organize the internal linkages and link text to suit the target search terms and their pages. If possible, organize links from other sites to suit the target search terms and their pages. Organize all the on-page elements to suit each page's target search term. Sit back and watch your rankings improve!