Many of the principles of external link building can also be applied to links within sites. The most important principle is to include keyphrases used for searchers within the anchor text of a hyperlink to point to relevant content. It’s also important to consider how to increase the number of internal links per pages which you want to rank well. A meshed structure within lots of internal links can work better than a simple hierarchy.
PageRank varies for pages across a site. The home page is typically highest, with each page deeper within the site having a lower PageRank. There are several implications of this. First, it is helpful to include the most relevant keyphases you want to target on the homepage or at the second level in the site hierarchy. Second, pages that feature in the main or secondary navigation (text link menu referencing the keyphase in the anchor text are best) are most likely to rank highly than the pages deeper in the site that don’t have many internal backlinks because they are not in the menu. Third, you need to review whether there are pages deeper within the site which feature products or services that are important, and which you need to rank for.
Chaffey, D. and Ellis-Chadwick, F., 2012. Digital marketing: strategy, implementation and practice (Vol. 5). Harlow: Pearson.