Internal linking and topical clusters

How much of a role do internal links play in creating topical clusters/content silos?

For context, I am working on improving my content scripts and right now I am focusing on creating clusters of related content. I am wondering how much of a role internal links play, my expectation is that they are crucial due to the way in which my site would be crawled, but I don't know for sure. Perhaps a decent related content widget would have the same effect without me going to the effort of working internal links into the script.

If internal links play a crucial role then what are people's feelings on where the links should be placed? i.e should the links be bi-directional or should they be one-way parent -> child or child -> parent .

I touched upon internal linking slightly in this thread, here are some rules I follow when linking internally:

• Vary anchor text
• Use majority of internal links in the bottom 40% of your page
• Maximum of 1 internal link per heading
• At least 1 heading space between internal links
• Longer content = allows for more internal links
• Dont dilute relevance by linking to content that is not semantically relevant to the page

I will be writing a more comprehensive guide on this soon.

* Internal linking is the practice of linking to other pages on your own website. This helps users and search engines navigate your site, find related content, and understand the hierarchy and relevance of your pages.Internal links also pass link equity (or PageRank) from one page to another, which can boost the ranking potential of your pages.

* Topic clusters are groups of interlinked pages that cover a broad topic and its related subtopics. For example, a topic cluster about SEO might include a pillar page that gives an overview of SEO, and cluster pages that cover subtopics like keyword research, link building, technical SEO.Each cluster page links to the pillar page and vice versa, creating a web of internal links that signals to search engines that your site is an authority on the topic.

Internal links could help all your pages get indexed faster for the most part
Use link whisper or YARPP