Internal linking is an important and often overlooked element of SEO and, unlike external links, the site owner has complete control over this, so it's crucial to make the most of it.
Scott Allen of Search Engine Guide has written a useful article on internal linking strategies. Here are a couple of his tips, alongside some from our SEO Best Practice Guide...
Link within your content
Scott advises webmasters to go through their site's content and work out where it would make sense to link to other pages which you want to rank better.
Make sure that the anchor text matches the keywords and phrases that you want the pages to rank well for. Scott also advises that these target keywords should appear on the destination page, as this will make the linking more effective.
Link from stronger pages
Some webpages may be more popular in the search rankings and receive more links than the rest of your website. You can strengthen these weaker pages by including some contextual links to them from the stronger pages.
Some additional tips from E-consultancy's SEO Guide...
Links from footers
This approach can also help with usability, as it is effectively a mini site map on every page. It also allows you to include some lengthy to be included.
For example, E-consultancy ranks well in Google for keyphrases such as 'web project management' and 'online surveys & research', both of which are included in the footer.
Spending time on an effective sitemap is not only effective for SEO, but also has usability benefits.
Always have a sitemap with text links, not images.
Make sure your anchor text reflects user behaviour and keyphrase analysis, so include not just product names, but also the most popular keywords for that page.
Links from e-newsletters and blogs
Articles in newsletters and blogs are another source of internal links and, as they are often hosted on separate or sub-domains, they may provide additional value.
Include relevant anchor text in the links back to the main site, not just the title of the article.