Every link on your own site is a small vote for how important a page is and what it's about, and most sites leave this almost entirely on autopilot.
Use Descriptive Anchor Text
"Click here" tells search engines nothing about the destination; anchor text that describes the linked page performs far better.
Connect New Content to Established Pages
When you publish something new, link to it from your strongest existing pages, and link back from the new page to relevant older content.
Audit for Orphan Pages
Pages with no internal links pointing to them are hard for crawlers and visitors alike to find, so check periodically for pages that have been cut off.
Next step: Use the Website Links Count Checker to see how many internal and external links a page currently carries before restructuring it.