When considering how to interlink, think of the user. If they would benefit from a link from one page to another then add it. Check your Analytics to see if the link gets used.
Recent example: a blog post on a particular topic proved popular, but was about to move into the blog archive as it was replaced by new content. I was worried about how Google might then perceive it in the site due to this. I looked through the site to find pages where it might make useful further reading, and updated those pages to reference the blog post. The month after I've done this the post is ranking as well as ever and has had more eyes on it throughout the site, increasing site 'stickiness' and increasing views of this page by 1/3.