DATA
Submit your website to “Google Search Console”
Why? After time you will get useful data in return (related to how your website is doing in the Google Results).
Potentially you’ll discover you are ranking for keywords you would not have thought about.
Get more indepth insights what you can learn from Google Search Console: here

Analytics
Google Analytics or Matomo or …

Testing
A/B Testing software.
Heatmap software: e.g. hotjar

Devices
Check on multiple devices (mobile, tablet, desktop).

Marketing
Installing pixels: Facebook, LinkedIn, …

Performance
usage of CDN: e.g. cloudflare.

Speed
You can check the load time of your website with https://tools.pingdom.com/ or https://www.webpagetest.org/

Legal
Cookie Policy, Privacy Policy, Terms and conditions
As it depends on where you live, contact a lawyer to make sure you are compliant

Consistency
Broken link checker

Keep them on your page
* Use open a new tab for external links (so your website stays open).
* Have call to actions
* Have “What’s next”, “Others also liked XYZ” kinda sections

Congruency
A (root) domain name can have multiple subdomains.
Technically spoken: stijnbernaer.com & www.stijnbernaer.com could be two different websites.
Also a website can be server insecure (http://) or over a secure connection (https://)
To not confuse users and the search engines, I recommend choosing one as your main website. E.g. stijnbernaer.com and serve that over https.
All possible ‘variants’ should be redirected to the main one.
So in the example above: http://stijnbernaer.com, http://www.stijnbernaer.com, https://www.stijnbernaer.com should be pointed to a single “version of the truth” https://stijnbernaer.com.
A way to quickly and easily test this is through https://wheregoes.com/

If you are using Cloudflare a way to “ban” http (port 80, insecure) is to put “Always Use Https” on ON.