Links (both onsite and offsite) are an important element of search engine optimization; in fact, they are possibly the most important element. However, in the quest to get more and more offsite links (which of course should not be neglected), many site owners and SEOs neglect internal linking.
In addition to creating a solid navigational system for your website, you should have an internal linking strategy – go through each page of content and see where you could logically insert contextual links, which is good for your site's overall SEO and for user navigation. This may seem basic, but many people forget about internal linking – and it is probably one of the easier SEO techniques.
Of course, building offsite links is still the number one way to reach page # 1 in the search engines and improve your website's ranking; however, since internal linking (also referred to as deep linking) is so simple it certainly should not be ignored. Especially if you have a blog or a website with lots of articles, since you can link to older relevant posts and articles.
Internal linking is also important because it will ensure that your website gets thoroughly crawled by the search engine's spiders by helping them find all the pages. It can also increase the relevancy and rank of individual pages for your keywords and even increase their PageRank. Moreover, it boosts your overall rankings to optimize all the pages on your website, and internal linking is one of the techniques that help with that.
Choose your anchor text just as carefully for internal links as you for offsite and external links. For instance, we use "Chicago SEO company" instead of the SEO Group to link to our homepage because that people are likely to search for when they are in need of search engine optimization and search engine marketing services (and of course, it is appropriate because we are an SEO company in Chicago).
In the end, internal linking alone will not get you to page # 1, but it is a fundamental element of your overall SEO and online marketing strategy, and certainly should not be overlooked.