SEO professionals often use checklists to make sure they don't miss anything which can help their client's site rank better. You can do the same thing with this checklist:
Your site should adapt to the visitors screen size.
Use Google's site speed test to ensure your site does not take longer than two to three seconds to load. You will receive helpful suggestions if it loads slowly.
This tells Google how to crawl your site. If you don't have one, there are free sitemap generators online.
Both encourage people to click on your link in the search results since they know exactly what they will find.
User one H tag and then H2 or H3 tags so people can scan your content and don't hit a giant wall of text. It also tells Google what is important on the page. You can, but you don't have to use keywords in the headers.
Use descriptive ALT tags for all images. You may rank better in Google images and you will definitely help visitors who use a screen reader.
Use an automated tool to find broken links on your site. Broken links offer a poor user experience and Google's looking at this now.
Get an SSL certification even if you don't feel you need one. People may get a security warning in their browser and avoid your site if you don't have one.
If you have a blog, look at your oldest content. If it's thin, consider removing it or re-wording it and adding on to the content.
Include contact information on your website to signal trust for Google and for visitors. For more information click here https://www.reddit.com/r/SEO/comments/ed8ajj/someofthebasicwebsiteandtechnical_seo/.